Small-angle x-ray scatterometry

ABSTRACT

A method for evaluating an array of high aspect ratio (HAR) structures on a sample includes illuminating the sample with an x-ray beam along a first axis parallel to within two degrees to the HAR structures in the array and sensing a first pattern of small angle x-ray scattering (SAXS) scattered from the sample while illuminating the sample along the first axis. The sample is illuminated with the x-ray beam along a second axis that is oblique to the HAR structures in the array, and a second pattern of the SAXS scattered from the sample is sensed while illuminating the sample along the second axis. Information is extracted with respect to the HAR structures based on the first and second patterns.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/254,281, filed Dec. 20, 2020, in the national phase of PCT PatentApplication PCT/IB2019/055735, filed Jul. 4, 2019, which claims thebenefit of the following U.S. provisional patent applications:

-   -   (a) U.S. provisional patent application 62/711,477 filing date        Jul. 28, 2018;    -   (b) U.S. provisional patent application 62/711,478 filing date        Jul. 28, 2018; and    -   (c) U.S. provisional patent application 62/711,476 filing date        Jul. 28, 2018.

FIELD OF THE INVENTION

The present invention relates generally to X-ray analysis, andparticularly to methods and systems for measuring geometrical structuresof semiconductor devices using X-ray scatterometry.

BACKGROUND OF THE INVENTION

X-ray scatterometry techniques are used for measuring geometricalstructures of semiconductor devices.

For example, U.S. Pat. No. 7,481,579 describes a method for inspectionthat includes directing a beam of X-rays to impinge upon an area of asample containing first and second features formed respectively in firstand second thin film layers, which are overlaid on a surface of thesample. A pattern of the X-rays diffracted from the first and secondfeatures is detected and analyzed in order to assess an alignment of thefirst and second features.

U.S. Pat. No. 9,606,073 describes apparatus that includes asample-support that retains a sample in a plane having an axis, theplane defining first, and second regions separated by the plane. Asource-mount in the first region rotates about the axis, and an X-raysource on the source-mount directs first and second incident beams ofX-rays to impinge on the sample at first and second angles along beamaxes that are orthogonal to the axis. A detector-mount in the secondregion moves in a plane orthogonal to the axis and an X-ray detector onthe detector-mount receives first and second diffracted beams of X-raystransmitted through the sample in response to the first and secondincident beams, and outputs first and second signals, respectively, inresponse to the received first and second diffracted beams. A processoranalyzes the first and the second signals so as to determine a profileof a surface of the sample.

U.S. Pat. No. 9,269,468 describes an X-ray optical device that includesa crystal containing a channel, which passes through the crystal and hasmultiple internal faces. A mount is configured to hold the crystal in afixed location relative to a source of an X-ray beam and to shift thecrystal automatically between two predefined dispositions: a firstdisposition in which the X-ray beam passes through the channel whilediffracting from one or more of the internal faces, and a seconddisposition in which the X-ray beam passes through the channel withoutdiffraction by the crystal.

U.S. Pat. No. 8,243,878 describes a method for analysis includingdirecting a converging beam of X-rays toward a surface of a samplehaving an epitaxial layer formed thereon, and sensing the X-rays thatare diffracted from the sample while resolving the sensed X-rays as afunction of angle so as to generate a diffraction spectrum including adiffraction peak and fringes due to the epitaxial layer.

Orientation of high aspect ratio holes High aspect ratio (HAR) holes areformed in semiconductor objects such as but not limited to semiconductorwafers. An aspect ratio (AR) is defined as the ratio of transverse(out-of-plane of the wafer) dimension of a hole to the lateral(in-plane) dimensions of a hole. A high aspect ratio may exceed 10:1.The lateral dimensions may be of sub-micron scale. The HAR holes may beunfilled or filled with materials that may differ from the compositionof the surrounding materials.

A stack (also referred to as a sequence) of HAR holes may provide astructure that has an aspect ratio that is higher than the AR of eachone of the HAR holes of the stack. When the HAR holes of the sequenceare identical and perfectly aligned then the AR of the sequence is thesum of ARs of the HAR holes.

Due to manufacturing process imperfections the HAR holes may be orientedin a manner that deviates from a desired orientation. The HAR holes maybe mutually misaligned.

Additionally or alternatively, at least one of the HAR holes may beorientated (in relation to the surface of the wafer) at an angle thedeviates from a desired angle of deviation. For example—while an HARhole should be normal to the surface of the wafer—the HAR hole may beoblique to the surface of the wafer.

There is a growing need to determine the orientations of HAR holes ofsequences of HAR holes that belong to an array of sequences, whereineach sequence includes HAR holes.

Extracting Information Related to an Array of High Aspect Ratio Holes.

Small angle x-ray scattering (SAXS) can be used to measure thearrangement and shape of an array of HAR holes on or withinsemiconductor samples. SAXS involves irradiating a semiconductor sample,wafer or coupon, with an x-ray beam. The x-ray beam passes through thesemiconductor sample and is scattered by the array of objects therebyproviding a scattered pattern (also referred to as a SAXS pattern orSAXS intensity distribution) that is sensed by a detector.

The array of objects may include, in addition to an array of HAR holes,one or more additional repetitive structure that includes a scatteredpattern that is generated due to scattering of the x-ray beam by thearray of the HAR holes, and by the one or more additional repetitivestructures.

There is a growing need to provide a system, method and a computerprogram product for extracting information about the array of HAR holes

Evaluating an Object from Different Angles

Small angle x-ray scattering (SAXS) can be used to measure thearrangement and shape of an array of HAR holes on or withinsemiconductor samples. SAXS involves irradiating a semiconductor sample,wafer or coupon, with an x-ray beam. The x-ray beam passes through thesemiconductor sample and is scattered by the array of objects therebyproviding a scattered pattern (also referred to as a SAXS pattern orSAXS intensity distribution) that is sensed by a detector

In some cases the semiconductor object should be measured from differentangles.

There is a growing need to provide a system and method for inspecting asemiconductor object from different angles in order to provide moreaccurate and precise shape information.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are schematic illustrations of small-angle X-ray scattering(SAXS) systems, in accordance with embodiments of the present invention;

FIG. 4 is a schematic illustration of a beam conditioning assembly, inaccordance with an embodiment of the present invention;

FIGS. 5 and 6 are schematic illustrations of slit assemblies, inaccordance with embodiments of the present invention;

FIGS. 7A and 7B are schematic illustrations of beam blocking assemblies,in accordance with embodiments of the present invention;

FIG. 8A is a schematic illustration of an image indicative of theintensity of an X-ray beam sensed by a detector without a beam blocker,in accordance with another embodiment of the present invention;

FIG. 8B is a schematic illustration of an image indicative of theintensity of an X-ray beam sensed by a detector in the presence of abeam blocker, in accordance with an embodiment of the present invention;

FIG. 9A is a schematic illustration of an image indicative of theintensity of a scattered X-ray beam sensed by a detector without a beamblocker, in accordance with another embodiment of the present invention;

FIG. 9B is a schematic illustration of an image indicative of theintensity of a scattered X-ray beam sensed by a detector in the presenceof beam blocker, in accordance with an embodiment of the presentinvention;

FIG. 10 is a schematic illustration of a scanning scheme in which anX-ray detector comprising an array of sensors is moved at steps smallerthan the inter-distance of the sensors, for improved angular resolution,in accordance with an embodiment of the present invention;

FIG. 11 illustrates a detector and a part of a slit assembly;

FIG. 12 illustrates a detector and a part of a slit assembly;

FIG. 13 illustrates a detector and a part of a slit assembly;

FIG. 14 illustrates a detector and a part of a slit assembly;

FIG. 15 illustrates a detector and a part of a slit assembly;

FIG. 16 illustrates a detector and a part of a slit assembly;

FIG. 17 illustrates a system and a detector;

FIG. 18 illustrates a system and a detector;

FIG. 19 illustrates a part of a system;

FIG. 20 illustrates a method;

FIG. 21 illustrates a sample, X-ray beam and a prior art XRF detector;

FIG. 22 illustrates XRF detectors;

FIG. 23 illustrates a sample, X-ray beam and an XRF detector;

FIG. 24 illustrates a sample and a detector;

FIG. 25 illustrates a sample and a detector;

FIG. 26 illustrates a system and a detector;

FIG. 27 illustrates a system and a detector;

FIG. 28 illustrates a system and a detector;

FIG. 29 illustrates a system and a detector;

FIG. 30 illustrates a system and a detector;

FIG. 31 illustrates a method;

FIG. 32 illustrates an array of aligned stacks of HAR holes and an arrayof misaligned stacks of HAR holes;

FIG. 33 illustrates an example of an aligned stack of HAR holes and amisaligned stack of HAR holes;

FIG. 34 illustrates an example of a 1D small-angle X-ray scattering(SAXS) pattern obtained when illuminating an array of stacks of HARholes;

FIG. 35 illustrates examples of relationships between rotations andintensity sum of different ranges of the SAXS pattern of an array ofaligned stacks of HAR holes;

FIG. 36 illustrates examples of relationships between rotations andintensity sum of different ranges of the SAXS pattern of an array ofmisaligned stacks of HAR holes;

FIG. 37 illustrates examples of relationships between rotations andintensity sum of a first range of SAXS patterns of an array ofmisaligned stacks of HAR holes and of an array of aligned stacks of HARholes;

FIG. 38 illustrates an example of a method;

FIG. 39 illustrates an example of a method;

FIG. 40 illustrates an example of semiconductor object;

FIG. 41 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus;

FIG. 42 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus;

FIG. 43 illustrates an example of a method;

FIG. 44 illustrates an example of semiconductor object;

FIG. 45 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus;

FIG. 46 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus;

FIGS. 47-52 illustrate examples of passage of x-ray beam cross sectionsand SAXS patterns; and

FIG. 53 illustrates an example of a 2D small-angle X-ray scattering(SAXS) pattern obtained when illuminating an array of two levels of HARholes.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Embodiments of the present invention that are described hereinbelowprovide improved methods and systems for analyzing geometrical featuresformed in various types of semiconductor devices and test structures.X-ray scatterometry techniques for analyzing features, such assmall-angle X-ray scattering (SAXS) methods, typically apply X-rayswhose wavelengths are on the order of one angstrom. Such wavelengths aresuitable for measuring High Aspect Ratio (HAR) features such as HARholes or trenches fabricated in semiconductor wafers. Measuringgeometrical and other properties of the features is carried out based onanalyzing the intensities of the X-rays scattered from the wafer atvarious angles.

In some embodiments, a SAXS system comprises a motorized stage, that isconfigured to move a planar sample, such as a wafer having front andback surfaces facing one another, wherein the front surface comprisesvarious types of features, such as HAR features. Additionally oralternatively, the back surface of the wafer may be patterned withsimilar and/or other types of features.

In some embodiments, the SAXS system comprises an X-ray source, that isconfigured to direct a beam of X-rays toward the back surface of thewafer. The SAXS system further comprises at least one detector, facingthe front surface of the wafer, the detector is configured to sense atleast part of the X-rays that have been scattered from and/ortransmitted through the wafer. The detector is configured to produceelectrical signals indicative of the intensity of the X-rays scatteredfrom HAR features in the front surface of the wafer, and received by thedetector.

In some embodiments, the SAXS system comprises a processor, that isconfigured to measure properties of the HAR features in question, basedon the electrical signals received from the detector.

In some embodiments, the SAXS system comprises a beam conditioningassembly, positioned between the X-ray source and the back surface ofthe wafer, and configured to adjust properties of the X-ray beam. Thebeam conditioning assembly comprises a crystal containing a v-shapedchannel having an entrance aperture, an exit aperture, and opposinginternal faces arranged so that the channel tapers from the entranceaperture to the exit aperture. The beam conditioning assembly furthercomprises an X-ray mirror, having a curved substrate with a multilayercoating. The mirror is configured to collect the beam and direct thecollected beam into the entrance aperture of the channel with a firstbeam diameter, so that the beam that is emitted from the exit aperturehas a second beam diameter, smaller than the first beam diameter.

In some embodiments, the SAXS system comprises a first slit, which ispositioned between the X-ray source and the back surface of the wafer soas to intercept the beam and to adjust spatial properties of theintercepted beam. The first slit comprises first and second movableblades that are typically not parallel to one another. The edges of thefirst and second blades are positioned in close proximity to one anotherso as to define the slit. In some embodiments, the processor isconfigured to move the edges of the first and second blades so as tocontrol spatial properties of the beam by adjusting the width of theslit.

In alternative embodiments, the SAXS system comprises a second slit,positioned between the X-ray source and the back surface of the wafer.The second slit comprises a movable blade having multiplescatterless-pinholes, each of which having a different width. Theprocessor is configured to position a selected scatterless-pinhole tointercept the beam by moving the movable blade, so as to control thespatial properties of the beam.

In some embodiments, the SAXS system comprises an optical gauge, that isconfigured to direct a light beam toward the back side of the wafer, tosense the optical radiation reflected therefrom using a detector, and,in response to the sensed optical radiation, to output, by the detector,a signal that is indicative of the position of the wafer. Based on thesignal, the processor is configured to estimate position parameters,such as the distance between the wafer and the detector, and theorientation of the wafer relative to the detector. The SAXS systemfurther comprises a motor, which is controlled by the processor so as toalign the orientation between the X-ray beam and the wafer in responseto the signal.

In some embodiments, the wafer comprises single-crystalline material,and the detector is configured to measure one or more beams diffractedfrom a lattice plane of the single crystal. The SAXS system furthercomprises a controller, that is configured to calibrate the position ofthe optical gauge relative to the lattice plane in response to themeasured diffraction. Based on the diffracted X-rays, the controller isfurther configured to measure the orientation of the wafer relative tothe detector, and to drive at least one motor to align the orientationbetween the wafer and the incident X-ray beam, based on the measuredorientation. In other embodiments, the processor may carry out at leastsome of the operations described above, instead of the controller.

In some embodiments, the SAXS system comprises a detector mounted on oneor more actuators, which are configured to move the detector withrespect to the scattered X-rays, over a range of positions on the frontsurface of the wafer, so as to measure the intensities of thetransmitted X-rays as a function of scattering angle. This configurationallows to measure the intensities of the transmitted X-rays withincreased angular resolution than is possible by the native resolutionof the detector elements. In some embodiments, the processor isconfigured to control the actuator, in response to electrical signalsproduced by the detector, so that the acquisition time of the detectorinversely depends on the intensity of the sensed X-rays.

In some embodiments, the detector comprises a two-dimensional array(also referred to as a matrix) of sensor elements having a predefinedpitch along height and width axes of the matrix. The actuator isconfigured to step the detector across the range of positions at a finerresolution than the predefined pitch along both height and width axes.

In some embodiments, the SAXS system comprises a beam blocker having oneor more beam stoppers. The beam blocker comprises a mount made of amaterial that is transparent to the X-rays. The one or more beamstoppers are held within the mount, and are made from a material atleast partially opaque to the X-ray beam. The beam blocker may bepositioned so that the one or more beam stoppers block the X-rays in apart of the range of angles, whereas the X-rays at the anglessurrounding the blocked part of the beam, pass through the mount to thedetector. In an embodiment, at least one of the beam stoppers has anellipsoidal shape with smooth edge so as to prevent scattering of thebeam from the beam stopper.

The disclosed techniques improve the sensitivity of SAXS systems todetect small geometrical changes in HAR features, by improving theangular resolution at which the X-ray beams scattered from HAR featuresare sensed by the detector. Moreover, the disclosed techniques may beused for reducing the footprint of SAXS systems while maintainingmeasurements in high sensitivity and resolution.

System Description

FIG. 1 is a schematic illustration of a small-angle X-ray scattering(SAXS) system 10, in accordance with an embodiment of the presentinvention. In some embodiments, SAXS system 10, also refers to herein as“system 10” for brevity, is configured to measure features on a sample,in the present example, a wafer 190, using scatterometry techniques, aswill be described hereinbelow.

In some embodiments, wafer 190 may comprise any suitable microstructureor materials, such as a single-crystal, a poly-crystal, an amorphousmicrostructure or any suitable combination thereof, such as differentmicrostructures or materials at different locations of wafer 190.

In some embodiments, system 10 comprises an X-ray excitation source,referred to herein as a source 100, driven by a high-voltage powersupply unit (PSU) 26. In some embodiments, source 100 is configured toemit an X-ray beam 130, also referred to herein as “incident beam 130”or “beam 130” for brevity, having a suitable energy to pass throughwafer 190.

In some embodiments, source 100 is configured to generate an intenseX-ray emission having a wavelength equal to or smaller than 0.1 nm withan effective spot-size of about 150 μm or less.

In some embodiments, source 100 may comprise any suitable type ofhigh-brightness X-ray source, such as, but not limited to (a) a fixedsolid anode, (b) a rotating solid anode, (c) a liquid metal, or (d) asynchrotron.

In some embodiments, the fixed solid anode-based source comprises amicro-focus X-ray tube in which high-energy electrons (>=50 keV) in avacuum are incident with a molybdenum (Mo) or silver (Ag) anode or anyother suitable metallic element or alloy. Such micro-focus X-ray tubesare provided by multiple suppliers such as, but not limited to, IncoatecGmbH (Hamburg, Germany), or rtw RÖNTGEN-TECHNIK DR. WARRIKHOFF GmbH &Co. (Berlin, Germany).

In some embodiments, the rotating solid anode micro-focus X-ray sourcemay comprise a Mo or Ag anode or any other suitable metallic element oralloy. Suitable rotating anode X-ray sources are provided by multiplesuppliers, such as, Bruker AXS GmbH (Karlsruhe, Germany).

In some embodiments, the liquid metal X-ray source comprises an anode ina molten state. The anode may comprise any suitable one or more elementsor alloys, such as alloys of gallium (Ga) and indium (In). A suitableliquid metal X-ray source may be selected, for example, from one or moreof the MetalJet products offered by eXcillum AB (Kista, Sweden).

In some embodiments, a synchrotron-based source that comprise a compactelectron accelerator-based X-ray source, such as the those provided byLyncean Technologies (Fremont, Calif. 94539, USA) and others beingdeveloped by the scientific community.

In some embodiments, wafer 190 may comprise a semiconductor wafer havingsurfaces 191 and 192. In some embodiments, surface 191 comprises highaspect ratio (HAR) features produced, on surface 191 and/or into thebulk of wafer 190 or materials deposited thereon, using any suitablesemiconductor processes, such as deposition, lithography and etching.Note that in these embodiments, surface 192 typically remains flat andsmooth and does not comprise HAR structures or another pattern producedby lithography and etching. It will be understood that during theproduction of features on surface 191, some layers may be deposited as ablanket on some locations of surface 192, e.g., using chemical vapordeposition (CVD) processes, and may cause some unintended topography onsurface 192.

In other embodiments, at least part of surface 192 may be patterned withthe aforementioned HAR features and/or with any other suitable types offeatures. In alternative embodiments, only surface 192 may comprise theaforementioned HAR features.

In the context of the present disclosure, and in the claims, the term“aspect ratio” refers to an arithmetic ratio between the depth and width(e.g., diameter in the case of a circular hole), or between the heightand width of a given feature formed in wafer 190. Furthermore, the term“high aspect ratio (HAR)” typically refers to an aspect ratio higherthan 10. The HAR structures, also referred to herein as HAR features,may comprise various types of three-dimensional (3D) structures formed,for example, on a logic device (e.g., a microprocessor), or a NAND flashmemory device, or a dynamic random-access memory (DRAM) device, or onany other device.

In some embodiments, the HAR features may comprise one or more Finfield-effect transistors (FETs), gate-all-around (GAA) FETs, nanowireFETs of a complementary metal-oxide semiconductor (CMOS) device, anaccess transistor of a DRAM device, one or more channels of a 3D NANDflash device, one or more 3D capacitors of a DRAM device, or any othertype of HAR feature.

In some embodiments, system 10 comprises a computer 20, which comprisesa processor 22, an interface 24 and a display (not shown). Processor 22is configured to control various components and assemblies of system 10described below, and to process electrical signals received from amovable detector assembly, referred to herein as a detector 240.Interface 24 is configured to exchange electrical signals betweenprocessor 22 and the respective components and assemblies of system 10.

Typically, processor 22 comprises a general-purpose processor withsuitable front end and interface circuits, which is programmed insoftware to carry out the functions described herein. The software maybe downloaded to the processor in electronic form, over a network, forexample, or it may, alternatively or additionally, be provided and/orstored on non-transitory tangible media, such as magnetic, optical, orelectronic memory.

In some embodiments, beam 130 is emitted from source 100 and passesthrough a shutter and slit assembly of system 10, referred to herein as“assembly 110,” made from any suitable material opaque to X-rays. Insome embodiments, processor 22 is configured to set the position ofassembly 110 using one or more controlled actuators, such as motors orpiezoelectric-based drives (not shown).

In some embodiments, assembly 110 is configured to improve the usersafety of system 10 by blocking any X-ray radiation deflected from thedesigned optical path of beam 130. In some embodiments, processor 22 isconfigured to adjust the position and size of the slits, so as tocontrol the divergence and spatial shape of beam 130.

In some embodiments, system 10 comprises additional slits, controlled byprocessor 22 for adjusting the divergence, intensity and spot-size ofbeam 130, and for blocking undesired scattered radiation.

In some embodiments, system 10 comprises a beam conditioning assembly,referred to herein as “assembly 165,” whose structure is described indetail in FIG. 4 below. In some embodiments, assembly 165 comprisesoptical elements, such as a mirror 120 and slits 125. Mirror 120 isconfigured to collect beam 130 from source 100 and assembly 110 andshape the optical properties of beam 130. For example, mirror isconfigured to produce a collimated beam or a focused beam, or acombination thereof (e.g., collimated in x-direction and focused iny-direction). Slits 125 are configured to adjust the properties of beam130, such as the divergence angle and the spot-size of the beam exitingmirror 120.

In some embodiments, beam conditioning assembly 165 may comprise avacuum chamber so as to prevent degradation of one or more of theaforementioned optical elements caused by the interaction between airand ionizing radiation on the surface of the optical elements.

In some embodiments, beam conditioning assembly 165 may have multipleconfigurations, some of which are described in detail in FIG. 4 below.For example, processor 22 may instruct beam conditioning assembly 165 toshape a first beam 130 as a collimated beam having a small spatialextent (i.e., spot size). Processor 22 may use this beam configurationfor measuring features disposed on a small sized test pad, as is thecase of logic applications in which metrology is performed on teststructures laid out in the scribe line between adjacent dies of wafer190.

In another example, wafer 190 may comprise a memory device (e.g., DRAM,NAND flash) having large arrays of repeating features (e.g., in thememory blocks), or a logic device having memory sections. In someembodiments, processor 22 may apply to a selected memory block of thedie, a second beam 130 having a larger spot size and higher intensitycompared to first beam 130. Processor 22 may exchange the mirror 122 tofocus beam 130 on the active surface of detector 240 so as to increasethe resolution of the respective SAXS system (e.g., system 10, 30, or 40described above).

In some embodiments, system 10 comprises a beam limiter, also referredto herein as a slit assembly 140, which comprises one or more slitsand/or movable blades described in detail in FIGS. 5 and 6 below. Slitassembly 140 is configured to control and/or refine the position and/orspot size and/or shape and/or convergence or divergence angle ofincident beam 130 on surface 192 of wafer 190.

In some embodiments, system 10 comprises a motorized rotation stage (notshown) having a rotation axis about the y-axis and centered at surface191. In some embodiments, source 100, beam conditioning assembly 165,and one or more of slit assemblies 110 and 140 are mounted on therotation stage, which is controlled by a motion controller and/or byprocessor 22.

In some embodiments, processor 22 may adjust or calibrate the anglebetween incident beam 130 and a normal to surface 192 of wafer 190, soas to improve the measurement conditions of system 10.

In some embodiments, system 10 comprises a chuck 200 having wafer 190mounted thereon. Chuck 200 is configured to mechanically support wafer190 and to allow directing beam 130 to most of the area (e.g.,excluding, at least some part of, the bevel of wafer 190 as shown inFIG. 1 ), or over the entire area of surface 192.

In some embodiments, chuck 200 may comprise a ring-shaped wafer support,but additionally or alternatively, chuck 200 may comprise any othersuitable design, such as a three-point kinematic mount.

In some embodiments, system 10 comprises a mount, for example, amotorized xyzχδφ-stage, referred to herein as “a stage 210,” havingchuck 200 mounted thereon. Stage 210 is controlled by processor 22 in axyz coordinate system of system 10, and is designed as an open frame(i.e., having no material in the center) so as to allow incident beam130 to directly impinge on surface 192 of wafer 190.

In some embodiments, stage 210 is configured to move wafer 190 relativeto beam 130 in x and y directions, so as to set a desired spatialposition of wafer 190 relative to incident beam 130. Stage 210 isfurther configured to move wafer 190 along z-axis so as to improve thefocus of beam 130 at the desired position on surface 192, or at anyother suitable position on wafer 190. Stage 210 is further configured toapply rotations χ and/or ω to about respective x-axis and y-axisparallel to surface 192 of wafer 190, and to apply azimuthal rotation φabout z-axis perpendicular to surface 192 of wafer 190.

In some embodiments, processor 22 is configured to select a predefinedazimuth φ so to align beam 130 with selected features in the structuresto be measured. For example, processor 22 may selected a first azimuthφ1 (not shown) so to align beam relative to line structures arranged ina one-dimensional (1D) on wafer 190. Moreover, processor 22 may select asecond azimuth φ2 (not shown) so to align beam 130 relative to a patternor arrays of holes or vias arranged in a two-dimensional (2D) pattern,such as rectangular or hexagonal lattice, on wafer 190.

In alternative embodiments, wafer 190 is mounted on a suitablestationary fixture (instead of stage 210), such that processor 22 canmove source 100, and the aforementioned assemblies (e.g., slit assembly110, and assemblies 165 and 140), so that the X-ray beam is directed toany one or more desired positions of wafer 190. In other embodiments,system 10 may comprise any other suitable set of mounts, such as a setof stages (e.g., a χωφ-stage for wafer 190, and a xyz-stage for theassemblies described above) and processor 22 is configured to movesurfaces 191 and 192 relative to beam 130 by controlling the set ofstages.

In some embodiments, incident beam 130 impinges on surface 192, passesthrough wafer 190 and is scattered from the aforementioned HAR featuresformed in surface 191 of wafer 190. In an alternative configuration ofwafer 190, surface 192 may comprise HAR features, in addition to orinstead of the HAR features patterned in surface 191, as describedabove. In this wafer configuration, incident beam 130 may also bescattered from the HAR features patterned on surface 192. In someembodiments, detector 240 of system 10 is configured to detect X-rayphotons scattered from the HAR features of both surfaces 191 and 192, aswill be described in detail below.

In some embodiments, incident beam 130 may impinge, at a point 111,perpendicular to surface 192 of wafer 190, or at any other suitableangle relative to wafer 190. In an embodiment, some of incident beam 130is absorbed as it traverses wafer 190 and a transmitted beam 220 exitssurface 191 of wafer 190 in the same direction of incident beam 130.Additional beams 222, scattered from the aforementioned one or more HARfeatures, exit at different angles to transmitted beam 130 relative tosurface 191 of wafer 22.

In some embodiments, detector 240 is configured to detect X-ray photonsof beams 222 impinging, at one or more regions 226, on a surface 224 ofdetector 240. Detector 240 may comprise any suitable type of one or moredetectors such as, but are not limited to, charge-coupled devices(CCDs), CMOS cameras provided by a number of suppliers, or arraydetectors made from a silicon (Si) or a cadmium telluride (CdTe)detection layer manufactured by DECTRIS Ltd. (Baden, Switzerland)supplying the 1D Mythen detectors and the 2D Pilatus and Eiger series ofdetectors.

In some embodiments, detector 240 may be mounted on a high-precisionmotorized translation and/or rotation stage (not shown), that isconfigured to move and/or rotate detector 240 based on predefined motionprofiles so as to improve the sensing efficiency thereof. Exampleimplementations of the stage and motion control of detector 240 aredescribed in detail in FIG. 10 below.

In some embodiments, the detectors described above are configured todetect X-rays beams scattered from wafer 190, referred to herein asbeams 222, and comprise sensitive elements of sufficiently small size soas to provide the necessary angular resolution for measuring thesmall-angle scattering intensity distribution from the HAR features ofwafer 190.

In some embodiments, system 10 comprises one or more calibration gauges215, used in calibrating and setting-up system 10, so as to accuratelymeasure properties of the aforementioned features patterned in wafer190. At least one of calibration gauges 215 is configured to produceelectrical signals indicative of the height and inclination of a givenposition at wafer 190 relative to a predefined reference, as will bedescribed in detail below. The electrical signals are sent, viainterface 24, to processor 22 for analysis.

In some embodiments, system 10 may comprise two calibration gauges 215.A first calibration gauge 215, facing surface 192 that is typically flatand has no HAR features or other types of patterns, and a secondcalibration gauge 215, facing surface 191 that is typically patternedand may also have the HAR features described above. In the exampleconfiguration of FIG. 1 , the second calibration gauge is optional andtherefore is shown as a dashed rectangle.

In other embodiments, system 10 may comprise any other suitableconfiguration of calibration gauges 215, for example, only the secondcalibration gauge facing surface 191, or having the aforementioned firstand second calibration gauges 215 facing surfaces 192 and 191,respectively.

In some cases, calibration gauge 215 may respond differently to theheight and inclination of a patterned surface (e.g., on surface 191) anda flat surface (e.g., non-patterned or blanket surface 192) of wafer190, and therefore, may require a calibration step before so as toimprove the accuracy of the height and inclination measurements.

In some embodiments, processor 22 may receive from the aforementionedsecond calibration gauge 215, signals indicative of the height andinclination of surface 191, which is patterned. The pattern may affect(e.g., induce shift in) the measurements carried out by the secondcalibration gauge. In these embodiments, processor 22 is configured toadjust or calibrate the angle between incident beam 130 and a normal tosurface 192 of wafer 190, so as to compensate for the pattern inducedshift, and therefore, to improve the quality of measurements carried outby system 10.

Note that when calibration gauge 215 measures the height and inclinationof surface 192, or of any other non-patterned surface, there istypically no shift in the measurements.

In some embodiments, calibration gauge 215, also referred to herein asan optical gauge, may comprise a light source and a sensor (not shown),or any other suitable configuration. Calibration gauge 215 is configuredto measure, at selected coordinates of the x and y axes, the localheight (e.g., distance along z-axis) and inclination of surface 192(e.g., relative to an x-y plane of the xyz coordinate system). In theseembodiments, the light source and the sensor are configured to operatein any suitable wavelength, e.g., visible, infrared (IR), or ultraviolet(UV), but typically not in the X-ray range.

In some embodiments, based on the electrical signals received fromcalibration gauges 215, processor 22 is configured to calculate anddisplay on the display of system 10, a 3D map indicative of the heightand inclination of surfaces 191 and 192, or any other selected plane ofwafer 10, relative to any suitable reference, such as the x-y plane ofthe xyz coordinate system. Processor 22 may calculate the 3D map basedon locations measured on surface 192, and additional locationscalculated between the measured locations, for example, by interpolatingthe height and inclination between two or more of the measuredlocations.

In some embodiments, processor 22 is further configured to determine theone or more starting positions for any X-ray-based alignment procedures.The alignments procedures are used to determine zero angles, referred toherein as ω0 and χ0, of beam 130 relative to one or more scatteringstructures in question by system 10.

In some embodiments, by independently measuring the orientation of (a)surfaces 191 and 192, and (b) scattering features in question (e.g., HARstructures) of wafer 190, relative to incident beam 130, processor 22 isconfigured to calculate the orientation of the scattering featuresrelative to surface 191 of wafer 190. This calculated orientation isparticularly important for measuring HAR structure, such as channelholes of 3D NAND flash memory.

In some embodiments, wafer 190 is typically grown on a crystal havingregular arrangement of the atoms comprising the crystal. Subsequently,wafer 190 is sliced from the crystal, such that the surface is alignedin one of several relative directions, referred to herein as the waferorientation. This is also referred to as the growth plane of thecrystalline silicon. The orientation is important for the electricalproperties of wafer 190. The different planes have differentarrangements of atoms and lattices, which affects the way the electricalcurrent flows in circuit produced in the wafer. The orientations ofsilicon wafers are typically classified using Miller indices, such as(100), (111), (001) and (110).

In some embodiments, system 10 may comprise an integrated opticalmicroscope 50, which may be used for navigation and pattern recognition,and in various other applications, such as optical inspection and/ormetrology, and/or for reviewing pattern and other features on wafer 190.

In some embodiments, optical microscope 50 is electrically coupled tocomputer 20 and is configured to produce signals indicative of thepattern in question, so that processor 22 could perform the patternrecognition or any other of the aforementioned applications.

Additionally or alternatively, system 10 may comprise other suitabletypes of integrated sensors (not shown) configured to provide system 10with complementary metrology or inspection capabilities.

In some embodiments, system 10 comprises one or more X-ray diffraction(XRD) detectors, such as XRD detectors 54 and 56, which are configuredto detect X-ray photons diffracted from planes substantiallyperpendicular to surfaces 191 and 192 of wafer 190.

Reference is now made to an inset 52, which is a top view of system 10.In some embodiments, XRD detectors 54 and 56 are arranged so as toproduce diffraction signal that may be used, as will be described below,for wafer alignment based on X-ray photons diffracted from some planesof the crystal lattice. Signals received from at least one of XRDdetectors 54 and 56 may also be used for other application.

The configuration of XRD detectors 54 and 56, optical microscope 50 andcalibration gauge 215 (optional) as shown in inset 52, is simplified forthe sake of conceptual clarity and is provided by way of example. Inother embodiments, system 10 may comprise any other suitableconfiguration and arrangement of sensors, detectors, microscopes andother suitable components and subsystems.

Reference is now made back to the side view of FIG. 1 . In someembodiments, processor 22 may receive from XRD detectors 54 and 56signals indicative of intensity of Laue diffraction from planessubstantially perpendicular to surfaces 191 and 192 of wafer 190. Forexample, crystallographic plane (555) is perpendicular to the surface ofa silicon wafer having a Miller index (001), referred to herein as Si(001). Additionally or alternatively, processor 22 may receive from atleast one of detectors 54, 56 and 240 signals indicative of theintensity of a first portion of beam 222 diffracted from any otherlattice plane of wafer 240. These signals are also referred to herein asdiffraction signals.

In some embodiments, processor 22 is configured to use X-rays diffractedfrom crystal planes substantially normal to surface 191 and sensed byXRD detectors 54 and 56, so as to determine the orientation of theincident beam and/or the direct beam, relative to the lattice planes ofa single-crystal wafer.

In other embodiments, detector 240 is further configured to sense theX-ray photons diffracted from the aforementioned Laue diffraction, andto produce signals indicative of the intensity of the sensed X-rayphotons. {Although this is not the case here, added this embodiment toblock engineering-around using a single detector for detecting alldiffracted and scattered X-ray photons}

In some embodiments, processor 22 may receive from detector 240 signalsindicative of the intensity of a portion of beam 222 transmitted throughsurface 192 and scattered from the HAR features of surface 191, alsoreferred to herein as scattered signals.

In alternative embodiments, calibration gauge 215 may comprise one ormore X-ray detectors, positioned to measure the Laue diffraction fromplanes substantially perpendicular to surfaces 191 and 192 of wafer 190,and to produce signals indicative of the intensity of the measured Lauediffraction, referred to herein as alternative diffraction signals.

In some embodiments, based on one or more of the diffraction signalsdescribed above, processor 22 is configured to instruct stage 210 toapply to and x rotations to wafer 190. Processor 22 may use a positionof wafer 190 corresponding to a maximal intensity of the diffractedX-ray detected by detector 240, for establishing the inclination anglesof beam 130 relative to the crystal lattice in wafer 190.

In these embodiments, processor 22 is configured to establish theinclination angle between the crystal lattice plane and the surface ofwafer 190, by using measurements at two or more azimuths that satisfythe diffraction condition. Moreover, processor 22 may apply to beam130X-ray diffraction (XRD) methods, for determining the orientation ofsurfaces 191 and 192, as a calibration technique for non-X-ray basedgauges. For example, calibration may be performed by measuring areference wafer, or any suitable reference mark mounted on a carrierwafer or on the tool, with known inclination angles between the crystallattice and surfaces 191 and 192.

In these embodiments, detector 240 may comprise various suitable typesof detection elements, such as but not limited to, (a) arrays of 1Ddiodes made from silicon, germanium or CdTe or other suitable materials,and (b) 2D X-ray direct or indirect detection cameras that are based onCCD, CMOS sensors, PIN diodes, or hybrid pixel detector technologies.

In alternative embodiments, system 10 may comprise, in addition tocalibration gauge 215, an energy dispersive X-ray (EDX) detectorassembly (not shown). The EDX detector assembly comprises asilicon-based or a germanium-based solid-state EDX detector, and anelectronic analyzer having a single-channel or multiple channels. TheEDX detector assembly is configured to measure X-ray fluorescenceemitted, for example, from point 111 of wafer 190, or from a predefinedlocation of a reference wafer used for calibrating system 10, and toproduce an electrical signal indicative of the intensity of X-rayfluorescence measured at point 11.

Based on the electrical signal, processor 22 is configured to determinea first position of point 111 and an offset between the first positionand a second position acquired at the same time, by calibration gauge215.

In some embodiments, X-ray source 100 and at least some of the x-rayoptics between source 100 and wafer 190, are mounted on a first stage,wafer 190 is mounted on a second stage (e.g., stage 210) and at leastone of optical microscope 50 and optical gauges 215 is mounted on athird stage. By comparing between the XRF-based and optical-basedsignals, processor 22 is configured to identify spatial offset, forexample, between an optical pattern recognition camera of opticalmicroscope 50, and X-ray beam 130, and to identify any misalignmentbetween the aforementioned stages of system 10.

In some embodiments, processor 22 is configured to estimate, based onthe received electrical signals, motion errors in stage 210, such asleadscrew errors and non-orthogonality between the x-axis and y-axis ofstage 210. Furthermore, based on the X-ray fluorescence signals,processor 22 is configured to calibrate stage 210, which calibration isalso referred to herein as stage mapping, by estimating offsets betweenone or more points in the coordinate system of system 10, and the actualpositions of the respective points on stage 210.

In some embodiments, system 10 may comprise, in addition to or insteadof the EDX assembly described above, a calibration scheme based onattenuation of the X-ray beam that passes through a suitable referencewafer (not shown), also referred to herein as a direct beam. Thesuitable reference wafer may comprise patterned features adapted toattenuate the direct beam intensity by several tens of percent, so thatdetector 240 could sense photons of the direct beam without beingaffected (e.g., saturated). In an exemplary embodiment, the referencewafer may comprise various patterns having any suitable thickness, e.g.,about 50 μm, of various suitable elements or alloys, such as but notlimited to tungsten (W), tantalum (Ta), gold (Au) or silver (Ag).

In some embodiments, processor 22 may use calibration gauge 215 foraligning between beam 130 and wafer 190 during measurements ofstructures on product wafers, such as wafer 190, or for calibratingsystem 10, e.g., after performing maintenance operations so as toprepare system 10 for use in production.

In alternative embodiments described above, system 10 may comprise atleast one calibration gauge 215 mounted at the opposite side of wafer190 so as to measure the inclination of wafer 190 based on signalssensed from surface 191. In an embodiment, processor 22 is configured tocalibrate an offset between the inclination angles measured on a blanketand the patterned area of a wafer.

In this embodiment, processor 22 positions calibration gauge 215 todirect the optical beam on a first point located adjacent to the edge ofsurface 191, which is typically blanket (i.e., without pattern), andmeasures the inclination of the wafer in x and y axes. Subsequently,processor 22 positions calibration gauge 215 to direct the optical beamat a second point on a pattern in the closest proximity (e.g., 10 mm-20mm) to the first point, and measures the inclination of the wafer in xand y axes.

In some embodiments, based on the inclination measurements at the firstand second points, processor 22 calculates the offset between theblanket and patterned surfaces. Note that the wafers are typicallyrigid, such that the actual inclination angle is not changing within adistance of 10 mm or 20 mm. The offset may be used as a calibrationfactor between inclination measurements on blanket and patternedsurfaces of wafer 190 or any other type of measured wafer. In someembodiments, processor 22 may set the spot size of the optical beam tobe sufficiently small to illuminate only the blanket surface near thewafer edge, but sufficiently large to average the inclinationmeasurement over various features of the pattern.

In some embodiments, wafer 190 comprises a single-crystalline material,and at least one of XRD detectors 54 and 56 is configured to measure thediffraction of beam 220 from a lattice plane of the single-crystalmaterial. In some embodiments, in response to the measured diffraction,processor 22 is configured to calibrate suitable parameters (e.g.,orientation) of calibration gauge 215 with respect to the lattice plane.

The particular configuration of calibration gauge 215 is shown in FIG. 1schematically, so as to demonstrate calibration techniques for improvingthe measurements of features, such as HAR structures, of wafer 190,carried out by system 10. Embodiments of the present invention, however,are by no means limited to this specific sort of example configuration,and the principles of calibration gauge 215 described above, may beimplemented using any suitable configuration.

In an embodiment, system 10 comprise a beam-blocking assembly, referredto herein as a beam blocker 230, made from an X-ray opaque orpartially-opaque material.

Beam blocker 230 is mounted in system 10 between wafer 190 and detector240, and is configured to occlude at least part of beam 220 fromirradiating detector 240. In some cases at least part of incident beam130 may be directly transmitted through wafer 190.

In some embodiments, beam blocker 230 may be positioned so as topartially block the directly-transmitted incident beam over an angularrange comparable to the spatial extent of incident beam 130.

Example implementations of beam blockers are depicted in detail in FIGS.7A and 7B below.

In some embodiments, the opaqueness level and shape of beam blocker 230affect the signals produced by detector 240, as depicted in FIGS. 8A,8B, 9A and 9B below.

In some embodiments, the detector assembly may comprise a singledetector, or an array of detectors arranged around regions 226. The beamdetectors may have a 2D configuration (i.e., an area detector), or a 1Dconfiguration (i.e., a linear detector), and are capable of countingX-ray photons. Detector 240 may be flat, or may have any suitable shapesuch as an arc angled toward beams 222 and 220. Responsively to thecaptured photons, 240 is configured to generate electrical signals,which are conveyed, via interface 24, to processor 22. One exampleimplementation of detector 240 is depicted in detail in FIG. 10 below.

In some embodiments, system 10 comprises a vacuum chamber 280, mountedbetween wafer 190 and detector 240 and configured to reduce undesiredscattering of beam 220 from air. In some embodiments, vacuum chamber 280comprises a metal tube with windows transparent to X-ray at each end, sothat beams 220 and 222 can pass between wafer 190 and detector 240.

In some embodiments, system 10 comprises a suitable vacuum pump, such asa roughing pump controlled by processor 22, so as to control the vacuumlevel in vacuum chamber 280, thereby to improve signal-to-background(SBR) ratio of X-ray photons impinging on the active surface of detector240.

In some embodiments, system 10 is configured to measure structural(e.g., dimensions and shape) as well as morphological parameters on theaforementioned features of wafer 190. For example, based on theelectrical signals received from detector 240, processor 22 isconfigured to measure a large variety of parameters, such as but notlimited to height, depth, width and sidewall angle of the patternedstructure, and thickness and density of films at any location acrosswafer 190.

In some embodiments, processor 22 comprises a model-based software foranalyzing the electrical signals received from detector 240. Processor22 uses a single structural model so as to simulate the X-ray scatteringfor all incidence angles having a common intensity normalization factor.Subsequently, processor 22 compares the correlation between the measuredand simulated intensity distributions, e.g., based on a numericalanalysis of a goodness-of-fit (GOF) parameter.

In some embodiments, processor 22 is configured to iteratively adjustthe parameters of the model, for example by using an algorithm such asDifferential Evolution (DE), so as to minimize the GOF parameter and toobtain the best-fit model parameters.

In some embodiments, processor 22 may reduce the correlation betweenmodel parameters by introducing into the model parameter values measuredby complementary techniques, for example the width at the upper layer ofa feature in question measured by a critical dimension scanning electronmicroscope (CD-SEM).

In some embodiments, system 10 may comprise one or more calibrationtargets having arrays of periodic features externally characterizedusing any suitable reference technique other than SAXS, e.g., atomicforce microscope (AFM). Processor 22 may use the calibration targets asa reference for calibrating the aforementioned assemblies of system 10and for alignment between (a) beam 130 and wafer 190, and (b) betweenbeam 222 and detector 240.

In some embodiments, based on the SAXS configuration and the softwarealgorithms described above, system 10 is configured to detect disorderparameters in the features in question across wafer 190. For example,horizontal and vertical roughness of the sidewalls and pitch variation,such as a pitch-walking error that may appear, for example, inmulti-patterning lithography processes or tilting and twisting of thechannel holes due to the etch process in 3D NAND memory.

The configuration of system 10 is shown by way of example, in order toillustrate certain problems that are addressed by embodiments of thepresent disclosure and to demonstrate the application of theseembodiments in enhancing the performance of such a system. Embodimentsof the present invention, however, are by no means limited to thisspecific sort of example system, and the principles described herein maysimilarly be applied to other sorts of X-ray systems used for measuringfeatures in any suitable type of electronic devices.

FIG. 2 is a schematic illustration of a SAXS system 30, in accordancewith another embodiment of the present invention. In some embodiments,the configuration of SAXS system 30, also refers to herein as “system30” for brevity, is similar to the configuration of system 10 with wafer190 tilted, also referred to herein as rotated, at any suitable angle(e.g., 45 degrees) relative to incident beam 130.

In some embodiments, processor 22 is configured to instruct stage 210 totilt wafer 190 about a tilt axis, such as azimuthal rotation to abouty-axis, in a plane of wafer 190, and to orient at least one of theaforementioned slit assemblies parallel to the tilt axis.

In some embodiments, system 30 is configured to measure structures ofwafer having a low aspect ratio (e.g., height over width ratio smallerthan ten). As described above, processor 22 is configured to rotatewafer 190 relative to incident beam 130, or alternatively, to rotateincident beam 130 relative to wafer 190. Processor is configured tocarry out the rotation over a range of several tens of degrees aroundy-axis, referred to herein as to rotation.

In some embodiments, the range of rotation angles may be symmetric, forexample ±50 degrees relative to the surface of wafer 190 shown, forexample, in FIG. 1 above. In alternative embodiments, processor 22 maycarry out asymmetric rotation (e.g., −10 degrees to +60 degrees), forexample by instructing stage 210 to rotate wafer 190 to a desired anglewithin the aforementioned range.

In some embodiments, processor 22 is configured to measure a profile ofa structures in more than one plane, for example, by rotating theazimuth of wafer 190 relative to beam 130. In the context of the presentdisclosure and in the claims, the term “profile” refers to a shape of asingle sidewall of a measured feature, or a change of width between twoadjacent sidewalls along the depth or height thereof or shift of thecenter of the hole as a function of depth. Additional asymmetry of theholes such as elliptical rather than circular cross section will usuallyrequire measurements at different azimuth and chi axes.

For example, processor 22 may measure the profile of a feature in aselected xy-plane using a series of intensity measurements carried outat different azimuthal angles. In some embodiments, processor 22 mayimplement this technique for measuring the diameter of a channel hole ina 3D NAND memory device, or the width of a via and/or metal line oflocal interconnect structures of a logic device.

In an embodiment, beam blocker 230 is positioned in close proximity todetector 240. In another embodiment, beam blocker 230 may be positionedin close proximity to wafer 190.

FIG. 3 is a schematic illustration of a SAXS system 40, in accordancewith another embodiment of the present invention. In some embodiments,the configuration of SAXS system 40, also refers to herein as “system40” for brevity, is similar to the configuration of system 10 with beamblocker 230 positioned in close proximity to wafer 190.

In some embodiments, processor 22 is configured to control the positionof beam blocker 230 at any suitable position along the path of beam 220,so as to reduce the level of undesired background and stray scatteringsensed by detector 240.

In some embodiments, processor 22 may set the position of beam blocker230 at one or more predefined mounting locations along the path of beam220. Additionally or alternatively, processor 22 may adjust the positionof beam blocker 230 by controlling a motorized stage (not shown)configured to move and hold beam blocker 230 at any suitable positionbetween wafer 190 and detector 240.

The structure of beam blocker 230 and related assemblies, such as theaforementioned stage, are described in detail, for example, in FIG. 7Abelow. Moreover, embodiments related to the functionality andapplications of beam blocker 230 in measuring features in question ofwafer 190 are described in detail in FIGS. 8B and 9B below.

The configurations of systems 10, 30 and 40 are provided by way ofexample. Embodiments of the present invention, however, are by no meanslimited to this specific sort of example systems, and the principlesdescribed herein may similarly be applied to other sorts of metrologysystems, such as but not limited to, reflection-based X-ray metrologysystems having both the X-ray source and detector assemblies located atthe same side of the wafer.

FIG. 4 is a schematic illustration of beam conditioning assembly 165, inaccordance with an embodiment of the present invention. Beamconditioning assembly 165 may be used in any of systems 10, 30 and 40described above, or in any other suitable configuration of a metrologysystem that applies X-ray beams for measuring features produced in wafer190 or any other type of wafer.

In some embodiments, beam conditioning assembly 165 comprises multiplesets of slit assemblies, referred to herein as assemblies 110, 300 and320. Note that as shown in FIGS. 1-3 , assembly 110 may be external tobeam conditioning assembly 165, or incorporated therein as shown in FIG.4 . Similarly, assembly 320 may be part of, or external to, beamconditioning assembly 165.

As described in FIG. 1 above, the slit assemblies of beam conditioningassembly 165 are configured to block undesired scattered X-ray radiationdeflected from the designed optical path of beam 130, and/or to adjustthe divergence, intensity and spot-size of beam 130.

In some embodiments, beam conditioning assembly 165 comprises mirror120, that is configured to shape the optical properties of beam 130after the beam passes through assembly 110, as described in FIG. 1above.

In some embodiments, mirror 120 comprises a curved substrate 122 coatedwith multiple layers 124, for example, alternating thin (e.g., an orderof one micron) layers of a heavy element, such as W, Mo or nickel (Ni),with a light element, such as carbon or silicon. Such mirrors for X-rayoptics are provided by several suppliers, such as Incoatec GmbH(Hamburg, Germany), AXO DRESDEN GmbH (Dresden, Germany) or Xenocs(Sassenage, France). In some embodiments, the configuration of mirror120 is adapted to provide a collimated beam in two directions (x,y). Inother embodiments, mirror 120 is configured to collimate beam 130 in onedirection (e.g., x-direction) and to focus beam 130 in an orthogonaldirection (e.g., y-direction).

In some embodiments, mirror 120 is configured to focus beam 130 onsurface 191, so as to obtain the smallest spot-size. In otherembodiments, focusing the X-ray beam on detector 240 may provide system10 with improved angular resolution of the X-ray beam sensed by detector240, e.g., in imaging of the HAR structures.

In case of a 2D collimated beam, beam conditioning assembly 165 maycomprise two optics, e.g., two mirrors 120, facing one another so as toincrease the solid angle (i.e., a two-dimensional angle) collected fromsource 100 and to increase the X-ray flux of beam 130.

In some embodiments, beam conditioning assembly 165 may comprise anysuitable configuration of multiple multilayered mirrors, such as mirror120, mounted on one or more motorized actuators controlled by processor22. Processor 22 may arrange the configuration of each mirror 120 ofbeam conditioning assembly 165, so as obtain the most suitablemeasurement conditions by adjusting the optical properties of beam 130.

In some embodiments, beam conditioning assembly 165 comprises a crystal310, made from a single crystal of germanium (Ge) or any other suitablematerial. Crystal 310 has a v-shaped channel 312 comprising an entranceaperture 316, an exit aperture 318, and opposing internal faces 314 and315 arranged so that channel 312 tapers from entrance aperture 316 toexit aperture 318, which is smaller than aperture 316.

In some embodiments, beam 130 passes through slit assembly 110 intomirror 120 and subsequently passes through slits assembly 300 andentrance aperture 316. Subsequently, beam 130 impinges on internal face314 and thereafter on internal face 316 and exits crystal 310 throughexit aperture 318.

In some embodiments, beam conditioning assembly 165 serves as adispersing element, and additionally as beam compressing opticconfigured to reduce the spot size of beam 130 after exiting slitassembly 320 of assembly 165. The configuration of beam conditioningassembly 165 enables the beam compressing, and yet, reduces the loss offlux compared to alternative techniques, such as a crystal with achannel having parallel faces or using one or more slits having one ormore narrow apertures.

In the example configuration of FIG. 4 , slit assemblies 110, 300 and320 are mounted before and after mirror 120 and crystal 310 so as toimprove the shaping of beam 130 along the optical path described above.In other embodiments, beam conditioning assembly 165 may comprise anyother suitable configuration of slit assemblies interposing betweensource 100 and mirror 120, and/or between mirror 120 and crystal 310,and/or between crystal 310 and slit assembly 140 or any other componentor assembly of any of systems 10, 30 and 40. For example, slit assemblymay be removed from the configuration of assembly 165 and may beexcluded from the configuration of any of systems 10, 30 and 40.

FIG. 5 is a schematic illustration of slit assembly 140, in accordancewith an embodiment of the present invention. As shown in FIGS. 1-3 ,slit assembly 140, also referred to herein as a beam limiter, ispositioned between source 100 and surface 192 of wafer 190, so as tointercept beam 130.

In some embodiments, slit assembly 140 comprises two or more movableplates 520 positioned along a translation axis 522 in a predefineddistance from one another so as to define a slit 512. The distancebetween plates 520 may be controllable by processor 22, for exampleusing one or more actuators (not shown) for moving one or more plates520 along translation axis 522. Alternatively, the distance betweenplates may be constant, e.g., by not moving plates 520 relative to oneanother, or by selecting a suitable type of slit 512 having staticplates positioned at a desired distance from one another.

In some embodiments, slit assembly 140 comprises two or more movableblades 510A and MOB, which are not parallel to one another and haverespective edges 514A and 514B positioned in close proximity to oneanother, so as to define a micro-slit 515.

In some embodiments, micro-slit 515 is configured to block part of beam130 that impinges on blades 510A and 510B without producing scatteredbeams, thus blades 510A and 510B are also referred to herein as“anti-scatter blades.” In some embodiments, blades 510A and 510B aremade from single-crystal materials such as tantalum (Ta), Ge,indium-phosphide (InP), or from polycrystalline materials such astungsten-carbide, and have a thickness of about 1 mm or any othersuitable thickness.

In the context of the present disclosure, and in the claims, the terms“single-crystal” and “mono-crystal” are used interchangeably and referto materials having a structure made from one crystal.

In some embodiments, slit assembly 140 comprises actuators 500A and500B, configured to move respective blades 510A and 510B alongrespective translation axes 516A and 516B, so as to adjust the width ofmicro-slit 515. In an embodiment, at least one of translation axes 516Aand 516B is substantially orthogonal to translation axis 522 in the x-yplane.

In some embodiments, actuators 500A and 500B comprise one or morepiezoelectric linear motors, for example the Piezo LEGS Linear 6G seriesprovided by PiezoMotor (Uppsala, Sweden) or similar products from othervendors such as Physik Instrumente (Karlsruhe, Germany). These motorscan be supplied with integrated high-resolution position sensors.

In some embodiments, processor 22 is configured to position slitassembly 140 in any suitable proximity to surface 192 of wafer 190. Thedesign of micro-slit 515 allows processor 22 to position slit assembly140 such that at least one of edges 514A and 514B is positioned at adistance smaller than ten millimeters (10 mm) from surface 192. In otherembodiments, processor 22 may position micro-slit 515 at any selecteddistance, e.g., between 100 mm and a few millimeters, from surface 192.

In some embodiments, the configuration of micro-slit 515 allowsprocessor 22 to position slit assembly 140 in close proximity (e.g.,down to a few millimeters) to surface 192 even when wafer 190 is tilted,as shown in FIG. 2 above.

In some embodiments, processor 22 is configured to set the distancesbetween (a) micro-slit 515 and surface 192, (b) edges 514A and 514B, and(c) plates 520, so as to obtain the desired optical properties of beam130 before impinging on surface 192 and interacting with the structuresand bulk of wafer 190.

Reference is now made to an inset 502, which is a top view of theinterception between slit assembly 140 and beam 130. In the example ofinset 502, processor 22 is configured to change the spatial shape ofbeam 130 from a round shape of a circle 524, to a rectangular shapeshown by a dashed rectangle 526, by moving (a) blades 510A and 510Balong respective translation axes 516A and 516B, and (b) plates 520along translation axis 522. Note that in this example, only the portionof beam 130 within the area of dashed rectangle 526 impinges on surface192, whereas the remaining part of beam 130, located between the edgesof circle 524 and dashed rectangle 526, is blocked by slit assembly 140.As described above and shown in inset 502, at least one of translationaxes 516A and 516B is orthogonal to translation axis 522.

The configuration of slit assembly 140 is simplified for the sake ofconceptual clarity and is provided by way of example. In otherembodiments, slit assembly 140 may comprise more than two blades 510Aand 510B, and/or more than two plates 520. Moreover, the edge of plates520 and/or edges 514A and 514B may have any suitable shape, for example,both plates 520 and edges 514A and 514B may have an arc intruding intothe area of the respective plates 520 and blades 510A and 510B, so as toform a round shape, rather than the aforementioned rectangular shape, ofbeam 130 exiting from slit assembly 140.

In other embodiments, translation axes 516A and 516B may be parallel ornot-parallel to one another, and at least one of translation axes 516Aand 516B may not be orthogonal to translation axis 522.

FIG. 6 is a schematic illustration of a slit assembly 150, in accordancewith another embodiment of the present invention. Slit assembly 150 mayreplace, for example, slit assembly 140 shown in FIGS. 1-3 .

In some embodiments, slit assembly 150 comprises a 3-pinhole collimationsystem, also referred to herein as apertures 604, 606 and 608, arrangedalong a translation axis 610 of a movable blade 550.

In some embodiments, slit assembly 150 comprises an actuator 600,configured to move blade 550 along translation axis 610.

Reference is now made to an inset 602, which is a top view of aninterception between beam 130 and blade 550.

In some embodiments, each aperture 604, 606 and 608 comprises a fixedsize aperture, such as a SCATEX scatterless pinhole produced by IncoatecGmbH (Hamburg, Germany) In the example of blade 550, apertures 604, 606and 608 have a round shape and each aperture has a different diameter,e.g., between about 20 μm and 500 μm.

In some embodiments, blade 550, which serves as a frame of thescatterless pinholes, is made from Ge for X-ray beams having low energyof photons, or from Ta for beams having photons with higher energies.

In some embodiments, the configuration of apertures 604, 606 and 608 isadapted to reduce undesired parasitic scattering typically occurs whenan X-ray beam passes through other types of apertures.

In some embodiments, actuator 600 may comprise any suitable type ofmotor coupled to a drive rod 620, that is configured to move blade 55along translation axis 610.

In other embodiments, the configuration of actuator 600 may be similarto the configuration of actuators 500A and 500B described in FIG. 5above.

In some embodiments, processor 22 is configured to determine the opticalproperties of beam 130 by instructing actuator 600 to position aselected aperture of blade 550 to intercept beam 130. In the example ofFIG. 6 , actuator 600 positions aperture 606 so that beam 130 passestherethrough, and the portion of beam 130 that exceeds the area withinaperture 606 will be blocked.

FIG. 7A is a schematic illustration of beam blocker 230, in accordancewith an embodiment of the present invention. In some cases, at leastpart of incident beam 130 that impinges on surface 192 is transmitteddirectly through wafer 190 and exits from surface 191, as part of beam220, without being scattered. The directly transmitted part of beam 220is referred to herein as a “direct beam.”

In some embodiments, beam blocker 230 is positioned so as to attenuatethe X-ray radiation of the direct beam, typically at the center of beam220. This attenuation is necessary, for example, to prevent damage todetector 240 and/or to prevent the detector from saturation and fromoperating in a non-linear region. On the other hand, too largeattenuation would eliminate the detection of essential signals that maybe used by processor 22 for tracking the angular position and intensityof the center of beam 220. Thus, the attenuation of beam blocker 230 istypically selected so that the intensity of the transmitted beam isattenuated to a few hundreds or thousands of photons per second atdetector 240.

In some embodiments, beam blocker 230 comprises one or more beamblocking elements, such as a beam stopper 232, typically having anellipsoidal-shape or any other suitable shape. In some embodiments, beamstopper 232 is made from an X-ray partially-opaque material, alsoreferred to as high-Z materials, typically comprising metal elements,such as tantalum or tungsten, and/or any suitable metal alloys.

As described above, the attenuation of beam stopper 232 is selected toenable reliable measurement of the angular position and intensity ofbeam 220, and at the same time prevent damage and non-linear distortionin the sensing of detector 240.

In some embodiments, beam stopper 232 is further configured to minimizebackground intensity from sources such as scattering with air orfluorescence and other scattering from the electronics behind the activeregion or surface of detector 240. Note that the active region ofdetector 240 may be partially illuminated due to the limited thicknessor low absorption of the detector material, e.g. 450 μm of silicon, withhigh energy X-rays having an energy of 10 keV or higher.

In some embodiments, beam stopper 232 has a curvy and/or smooth edge soas to reduce the scattering intensity of the direct beam.

In some embodiments, beam blocker 230 comprises a matrix 236, alsoreferred to herein as a mount. Matrix 236 is made from a block ofmaterial adapted not to scatter X-rays, such as, but not limited to,diamond or polymers such as thin-sheets of biaxially-orientedpolyethylene terephthalate (BoPET) polyester, also referred to herein asMylar™, or poly (4,4′-oxydiphenylene-pyromellitimide) polyimide, alsoreferred to herein as Kapton®.

In some embodiments, beam stopper 232 is mounted in a recess (not shown)formed in a matrix 236, and is mechanically supported by the matrixmaterial without using an adhesive that may scatter X-rays, andtherefore, may increase the level background signals to themeasurements. Since adhesives may degrade under X-ray irradiation withtime, absorbing features can be fabricated using techniques used forelectronics manufacturing such as depositing thin adhesion and seedlayers with appropriate metallization and then electroplating a thickX-ray absorbing material such as gold (Au), or by using of additiveprinting techniques using inks incorporating a high concentration ofmetallic nanoparticles followed by an annealing process.

In other embodiments, beam stopper 232 may be coupled to matrix 236using any other suitable technique, such as an adhesive that does notscatter X-rays. Note that beam stopper 232 is adapted to attenuate thedirect beam, such that the surrounding scattered beam, shown in FIG. 1as beam 222, is not attenuated since the support structure istransparent to the scattered X-rays of beam 222.

In some embodiments, the material of beam stopper 232 allows sufficientintensity of the direct beam to be partially transmitted, so thatprocessor 22 may determine the intensity and position of the direct beamsensed by detector 240 without moving beam stopper 232 away from thedirect beam.

In some embodiments, beam blocker 230 comprises a mount, also referredto herein as a high-precision motorized stage 233, which is controlledby processor 22 and is configured to move along one or more axes. Forexample translation x-axis and y-axis in the configuration of systems 10and 30 shown, respectively, in FIGS. 1 and 2 above.

In some embodiments, matrix 236 is mounted on stage 233 so thatprocessor 22 sets the position of beam stopper 232 relative to thedirect beam transmitted through wafer 190. In other embodiments, stage233 may comprise rotational axes (not shown) so as to improve thealignment of beam stopper 232 with beam 220, and particularly with thedirect beam thereof. In another embodiment, stage 233 is also configuredto move in z-axis so as to enable the configuration of system 40, shownin FIG. 3 above, or to further improve the attenuation level of thedirect beam.

In some cases, the attenuation of the direct beam may be sufficientlyhigh by wafer 190 or by any other element of system 10. Thus, in otherembodiments, processor 22 is configured to move beam blocker 230 awayfrom the path of beam 220. In these embodiments, beam stopper 232 is notintercepting beam 220, so that processor 22 may monitor the intensityand position of the direct X-ray beam, based on the direction andintensity of the direct beam sensed by detector 240.

The configuration of beam blocker 230 is simplified for the sake ofconceptual clarity and is provided by way of example. In otherembodiments, beam blocker 230 may comprise any other suitable componentsand/or assemblies arranged in any other suitable configuration forattenuating the intensity of the direct beam and/or for managing thesensing of one or more beams 222 scattered from wafer 190. For example,the beam-blocker may comprise multiple beam stoppers 232, or two narrowwires whose separation can be adjusted so as to change the effectivewidth of the blocker.

FIG. 7B is a schematic illustration of beam blocker 330, in accordancewith an embodiment of the present invention. Beam blocker may replace,for example, beam blocker 230 of FIG. 1 above. In some embodiments, beamblocker 330 comprises a matrix 333 made from a synthetic diamond, or thematerials of matrix 236 described above, or any other suitable materialadapted not to scatter X-rays of beam 220.

In some embodiments, beam blocker 330 comprises multiple types of beamstoppers, each of which made from a suitable material. For example, agold-based beam stopper having a thickness of about 50 μm, or any othersuitable thickness, or a tungsten-based beam stopper having a typicalthickness between 50 μm and 100 μm, or any other suitable thickness. Thetungsten-based beam stopper may be produced, for example, by lasercutting of a suitable tungsten foil.

In some embodiments, the beam stoppers are coupled to matrix 333, usingany suitable technique, such as recessing the matrix and disposing thebeam stopper into the recessed pattern, or any other suitable method,such as those described in FIG. 7A above. For example, gold may bedeposited into the recessed pattern, and the laser-cut tungsten pieces,described above, may be attached to the recessed pattern.

In some embodiments, beam blocker 330 comprises multiple geometricshapes and arrangements of beam stoppers. In the example of FIG. 7B,beam blocker 330 comprises five bar-shaped beam stoppers arranged in arow along X-axis, at a 5 mm distance from one another, and having asimilar length (measured along Y-axis) of about 10 mm. The bar-shapedbeam stoppers have different width, e.g., between 0.1 mm and 0.5 mm. Forexample, beam stoppers 332 and 334 have a width (measured along X-axis)of about 0.5 mm and 0.3 mm, respectively, and the bar between beamstoppers 332 and 334 has a width of about 0.4 mm.

In some embodiments, beam blocker 330 comprises five square-shaped beamstoppers having the same arrangement along X-axis (e.g., width anddistance) of the bar-shaped beam stoppers described above. For example,beam stoppers 336 and 338 have widths of 0.4 mm and 0.2 mm,respectively, and the square-shaped beam stopper laid out therebetweenhas a width of 0.3 mm.

In some embodiments, beam blocker 330 may comprise other shapes of beamstoppers. For example, T-shaped beam stoppers 335 and 339, and L-shapedbeam stoppers 337, all arranged in any suitable orientation and havingany suitable width, length and distance from one another. In the exampleof FIG. 7B, the T-shaped and L-shaped beam stoppers have a typical widthof 0.2 mm, length between 1 mm and 2 mm, and distance of about 5 mmbetween adjacent beam stoppers. Additionally or alternatively, theT-shaped and L-shaped beam stoppers may be used as alignment marks foraccurately positioning a selected beam stopper to block the beamdescribed above.

The configuration of beam blocker 330 is provided by way of example. Inother embodiments, beam blocker 330 may comprise any other set of beamstoppers, having any suitable shape and dimensions and arranged in anysuitable layout.

FIG. 8A is a schematic illustration of an image 402 indicative of theintensity of beam 220 sensed by detector 240 in the absence of beamblocker 230, in accordance with another embodiment of the presentinvention. In the example of FIG. 8A, incident beam 130, which iscollimated in both x-axis and y-axis, impinges on wafer 190 comprising ahexagonal array of features, such as HAR capacitors of a DRAM device.

In some embodiments, image 402 comprises a spot 420, indicative of theintensity of the direct beam sensed by detector 240. Image 402 furthercomprises multiple spots 410, indicative of respective beams 222scattered from the hexagonal array of the DRAM device. In someembodiments, the gray level of spots 410 and 420 is indicative of theintensity of beam 220 (e.g., flux of photons and respective energythereof) sensed by detector 240. In the present example, white color isindicative of high intensity, and darker colors indicative of lowerintensities sensed by detector 240.

In some embodiments, image 402 comprises locations 404 positionedbetween spots 410 and spot 420, within region 226 of detector 240, alsoshown in FIG. 1 above. Image 402 further comprises a region 400,referred to herein as a background, located out of region 226 ofdetector 240.

In some embodiments, processor 22 is configured to set the properties ofbeam 130, such that (a) spots 410 have coherent scattering, andtherefore appear bright, (b) locations 404 between spots 410 haveincoherent scattering, and therefore appear darker than spots 410located within a virtual circle 405 surrounding an area in closeproximity to spot 420, and (c) region 400 has no scattering, or ascattering level below a predefined threshold, and therefore appears inblack.

In some embodiments, in the absence of beam blocker 230, the highintensity of the direct beam causes saturation of detector 240 at thearea of spot 420, and therefore, non-linear sensing across region 226.Therefore, spot 420 appears in white color and the area within circle405 appears substantially brighter than the peripheral area of region226.

As described above, due to the coherent scattering, spots 410 appearbrighter than locations 404 within the area of circle 405. However, dueto the increase in the incoherent background from detector 240, spots410 appear darker than locations 404 at the periphery of region 226.Thus, the reliable sensing area of detector 240 is limited to the areawithin circle 405, subject to the limited contrast caused by theincreased background (incoherently X-ray intensity) from detector 240.

FIG. 8B is a schematic illustration of an image 406 indicative of theintensity of beam 220 sensed by detector 240 in the presence of beamblocker 230, in accordance with an embodiment of the present invention.Similar to the example of FIG. 8A, incident beam 130, which iscollimated in both x-axis and y-axis, impinges on wafer 190 comprisingthe hexagonal array HAR capacitors of the aforementioned DRAM device.

In some embodiments, image 406 comprises a spot 430, indicative of theintensity of the direct beam sensed by detector 240. Image 406 furthercomprises multiple spots 440, indicative of respective beams 222scattered from the hexagonal array of the DRAM device.

In some embodiments, beam blocker 230 attenuates the intensity of thedirect beam sensed by detector 240, therefore, spot 430 appears in adark gray color and detector 240 does not introduce a significantbackground intensity shown, for example, in FIG. 8A above.

In some embodiments, the sensed intensity of the coherent scatteringfrom the HAR features appears stronger within circle 405 compared to theperiphery of region 226. Yet, the linear sensing of detector 240 reducesthe intensity detected from locations 404 to the background level ofregion 400. Thus within region 226, the contrast between all spots 440and regions 404 is sufficiently high to conduct measurements at highaccuracy and precision. The term “accuracy” refers to measuring theactual size of the feature in question, and the term “precision” refersto the repeatability of multiple measurements carried out on a givenfeature in question.

In some embodiments, the presence of beam blocker 230 allows processor22 to monitor the partially attenuated direct beam (e.g., during themeasurements of the HAR structures) so as to control parametersindicative of the properties of beams 130 220, such as the incident fluxof both beams 130 and 220 at respective positions on wafer 190 anddetector 240.

FIG. 9A is a schematic illustration of an image 502 indicative of theintensity of beam 220 sensed by detector 240 in the absence of beamblocker 230, in accordance with another embodiment of the presentinvention. In the example of FIG. 9A, incident beam 130, which iscollimated in x-axis and focused on wafer 190 (e.g., on surface 191) iny-axis, impinges on wafer 190 comprising an array of 1D (lines) or longand narrow 2D features, such as lines or trenches in a device ordedicated metrology pad in the scribe-line or elsewhere on die.

In some embodiments, image 502 comprises a spot 526, indicative of theintensity of the direct beam sensed by detector 240. Image 502 furthercomprises multiple features 510, indicative of respective beams 222scattered from the array. In some embodiments, the gray level offeatures 510 and spot 526 is indicative of the intensity of beam 220sensed by detector 240. As described in FIG. 8A above, white color isindicative of high intensity, and darker colors indicative of lowerintensities sensed by detector 240.

In some embodiments, image 502 comprises locations 504 positionedbetween features 510 and spot 526, within region 226 of detector 240.Image 502 further comprises region 400, located out of region 226 ofdetector 240.

In some embodiments, processor 22 is configured to set the properties ofbeam 130, such that features 510 have coherent scattering, locations 504have incoherent scattering, and region 400 has no scattering.

In some embodiments, in the absence of beam blocker 230, the highintensity of the direct beam causes sufficiently high backgroundintensity and loss of contrast across region 226. Therefore, spot 526appears in white color and the area within a virtual rectangle 505appears substantially brighter than the peripheral area of region 226.

As described above, due to the coherent scattering, features 410 appearbrighter than locations 504 within the area of circle 405. However, theincreased background from detector 240, results in loss of contrast atthe periphery of region 226. Thus, the reliable sensing area of detector240 is limited to the area within rectangle 505. Note that in theabsence of beam blocker 230, the shape and size of the reliable sensingarea of detector 240 depends on the type (e.g., geometry) of themeasured features (e.g., round in FIG. 8A and linear in FIG. 9A), theproperties of beam 130, and other parameters of the system, such as thetilt angle of wafer 190 shown, for example, in system 30 of FIG. 2above.

FIG. 9B is a schematic illustration of an image 506 indicative of theintensity of beam 220 sensed by detector 240 in the presence of beamblocker 230, in accordance with an embodiment of the present invention.In some embodiments, processor 22 sets incident beam 130 in a likemanner to the setting described in FIG. 9A above. Therefore, beam 130,which is collimated in x-axis and focused in y-axis, impinges on wafer190 comprising the aforementioned layout of the lines or trenches.

In some embodiments, image 506 comprises a spot 530, indicative of theintensity of the direct beam sensed by detector 240. Image 506 furthercomprises multiple features 540, indicative of respective beams 222scattered from the array of the NAND flash memory device.

In some embodiments, beam blocker 230 attenuates the intensity of thedirect beam sensed by detector 240, therefore, spot 530 appears in adark gray color and detector 240 is not saturated by excess intensity.

In some embodiments, the sensed intensity of the coherent scatteringfrom the lines or trenches, appears stronger within rectangle 505compared to the periphery of region 226. Yet, the linear sensing ofdetector 240 reduces the intensity detected from locations 504 to thebackground level of region 400. Thus within region 226, the contrastbetween all features 540 and regions 504 is sufficiently high to conductmeasurements at high accuracy and precision.

As described in FIG. 8B above, the presence of beam blocker 230 allowsprocessor 22 to monitor the partially attenuated direct beam so as tocontrol parameters indicative of the properties of beams 130 220.

FIG. 10 is a schematic illustration of a scanning scheme in whichdetector 240 comprising an array of sensors 243 is moved at stepssmaller than the inter-distance of the sensors, for improved angularresolution, in accordance with an embodiment of the present invention.In some embodiments, detector 240 comprises an array of 1D or 2D sensorelements, referred to herein as sensors 243. In the example of FIG. 10detector 240 comprises 2D sensors 243, each of which has a predefinedpitch in x-axis and in y-axis, referred to herein as Px and Py,respectively.

In the context of the present disclosure, and in the claims, the terms“Px” and “width axis” are used interchangeably, and the terms “Py” and“height axis” are also used interchangeably. In some embodiments, eachsensor 243 is configured to produce electrical signals indicative of theintensity of the direct beam and of beam 222 impinging on the activesurface thereof. In some embodiments, processor 22 is configured toproduce an image, referred to herein as a pixel, based on the electricalsignals received from each sensor 243. Thus, the size of each pixel in xand y axes is typically on an order of Px and Py, respectively.

In some embodiments, detector 240 is mounted on a motorized stage 246comprising translation and rotation motors (not shown). In someembodiments, the translation motors are configured to move detector 240in x-axis and y-axis for scanning in the x-y plane, and in z-axis forimproving the focus of beam 222 on the active surface of sensors 243. Insome embodiments, the translation motors are configured to rotatedetector 240, for example about z-axis, for aligning sensors 243 withthe direction of the scattered X-ray photons of beam 222.

In some embodiments, stage 246 comprises high-precision encoders and/orinterferometers (not shown) configured to measure the translation androtation positions of the respective axes of stage 246 at a predefinedfrequency.

In some embodiments, system 10 may comprise a motion control assembly(not shown), which is controlled by processor 22. The motion controlassembly comprises a controller (not shown) configured to determine, foreach motor, a respective motion profile (e.g., speed, acceleration anddeceleration). The motion control assembly further comprises one or moredrivers, which are controlled by the aforementioned controller and areconfigured to drive the motors of stage 246 to move in accordance withthe respective motion profile and based on the current position measuredby the respective encoder or interferometer of each axis.

In other embodiments, processor 22 is further configured to control themotion of stage 246, and may be used for this purpose, in addition to orinstead of the controller.

In some embodiments, stage 246 is configured to move detector 240 alongx-axis and y-axis in selected respective step sizes, referred to hereinas Dx and Dy, which are typically substantially smaller than respectivePx and Py. Thus, stage 246 is configured to move detector 240 in stepsequal to a fraction of the pixel size described above.

Equations 1 and 2 below provide explicit expressions for estimating thesize of Dx and Dy, respectively:Dx=ρ _(x) /m  (1)Dy=ρ _(y) /n  (2)

where n and m are typically integer numbers indicative of the selectedstep size in x-axis and y-axis, respectively.

In some embodiments, processor 22 is configured to receive theelectrical signals produced by a given sensor 243, and to set therotation speed of wafer 190 in response to the received signals. Notethat the acquisition time of sensor 243 inversely depends on theintensity of the sensed X-rays. For example, if the electrical signalsreceived at a given area of wafer 190 are indicative of a relatively lowintensity of the sensed X-rays, processor 22 may instruct the controllerto decelerate the motion of detector 240 at the given area so as toincrease the flux of photons and thereby to increase the SBR sensed atthe given area.

Similarly, in case of a relatively high intensity of the sensed X-raysat different rotation angles of wafer 190, processor 22 may instruct thecontroller to accelerate the motion of detector 240 at the differentarea so as to increase the measurement throughput.

In some embodiments, processor 22 or a controller of detector 240 isconfigured to control the acquisition time so that detector 240 receiveda predefined intensity range across the measured positions on wafer 190.The predefined intensity range enables sufficient intensity to obtainhigh SBR, and yet, prevents saturation and non-linear sensing in therespective sensors of detector 240.

In some embodiments, processor 22 is configured to acquire, from a givensensor 243, an image based on the intensity of the scattered photons ofbeam 222, at an acquisition time, t. Therefore, in an array of an n-by-msub-pixels, processor 22 allocates for each sub-pixel a uniform timeinterval of t/(m×n), so as to acquire n-by-m sub-images within theacquisition time t.

In some embodiments, processor 22 is configured to move detector 240 ina raster pattern along the x and y axes using respective step sizes Dxand Dy, so as to measure the intensity distribution of each timeinterval at a different position of detector 240 spanning the total areaof a single pixel.

In some embodiments, processor 22 is configured to combine the n-by-msub-images received from the respective sensor 243, into a single pixel.Processor 22 may apply to the received sub-images any suitable method,such as but not limited to, a simple arithmetic interpolation, or anysuitable image processing algorithms, so as to increase the resolution(e.g., angular resolution) of the combined image.

In some embodiments, by applying the sub-pixel stepping and combiningthe n·m sub-images to form a single image having improved angularresolution, processor 22 overcomes a resolution limitation of SAXSsystems caused by the available pixel size of the respective detectorassembly.

Equation (3) below provides an expression for calculating the angularresolution Δθ of a detector having a pixel size p, positioned at adistance d from the wafer in question:Δθ=p/d  (3)

Based on a typical pixel size of 172 um a distance of about 5-6 metersis required to obtain an angular resolution on an order of 0.3 mrad-0.5mrad.

In some embodiments, by using the sub-pixel stepping and combining then×m sub-images, as described above, the designed distance betweendetector 240 and wafer 190 may be reduced, for example by a factor ofthree, e.g., to less than two meters, while maintaining the requiredangular resolution.

In some embodiments, processor 22 is configured to reduce the overallcycle time of measuring the features in question of wafer 190 byincreasing the speed of detector 240 to the maximal level that enablesacquiring the sub-images at sufficiently-high SBR as will be describedin detail hereinbelow.

The intensity of scattered beam 222 typically depends on the Fouriertransform of the electron density distribution ρ(r) of the scatteringobjects. For weak scattering, the scattered amplitude “A” may becalculated using equation (4):A(Q)∝∫_(V)ρ_(e)(r)exp(−iQ·r)dr  (4)

where Q is the scattering vector and is determined by X-ray wavelength λand the respective angles of incident beam 130 and scattered beam 222relative to wafer 190.

Equation (5) below provides a well-known expression for calculating thescattered intensity in the kinematical approximation:I(Q)=(|A(Q)|)² +Ib(Q)  (5)

where Ib(Q) is an incoherent “background” intensity contribution systemof any origin such as fluorescence or scattering from structures in thewafer beyond the coherence length of the radiation or parts of the tool,i.e. slits or beam blocker.

The electron density ρ_(e) is related to a refractive index “n” of thescattering objects of wafer 190. Equation (6) below provides anexpression for calculating the refractive index n:n=1−δ−iβ  (6)

Where δ and β are, respectively, the dispersive and absorptivecomponents of the wave-matter interaction.

Note that the value of the refractive index is close to unity for allmaterials in the range of hard X-rays, where the value of δ is on theorder of 10⁻⁶.

Therefore, equation (7) below may be used for calculating the electrondensity ρ_(e):

$\begin{matrix}{\rho_{e} = {\frac{2\pi}{\lambda^{2}r_{e}}\delta}} & (7)\end{matrix}$

where r_(e) is the value of a classical electron radius, equals to2.818×10⁼¹⁵ meters.

In some embodiments, processor 22 is configured to calculate a physicalmodel comprising the topography and the materials of the features inquestion described above. Processor 22 is configured to compare betweenthe calculated and measured intensities using any suitable parameters,such as a numerical goodness-of-fit (GOP), and to adjust the modelparameters so as to minimize the different between the calculated andmeasured data.

The dataset fitted by processor 22 may comprise one or more 1D datasets,such as the intensity distribution integrated along or across thediffraction peaks for different orientations of beam 130 and/or detector240 relative to wafer 190, or a series of 2D images of the scatteredintensity patterns or a combination thereof.

As described above, processor 22 is configured to reduce the measurementtime of the features in question by acquiring data using differentacquisition times at different locations across wafer 190. In someembodiments, processor 22 may apply the different acquisition time bydetector 240 in various conditions. For example, when measuringdifferent type of features (e.g., geometrical structure and/ormaterials), and/or layout (e.g., a single feature, or a dense array offeatures), and/or the angle between beam 130 and surface 192 of wafer190, and/or the angle between beam 222 and the active surface ofdetector 240.

In some embodiments, processor 22 is configured to adjust the signalacquisition time so as to obtain sufficient intensity that enablessufficiently high SBR of the electrical signals received from detector240. The measurement uncertainty of scattered X-ray having an averageintensity based on N counts is typically dictated by Poisson countingstatistics such that the standard error is given by IN and thefractional error is given by VON). Therefore, processor 22 may reducethe measurement uncertainty by increasing the number of counts.

As described above, processor 22 may reduce the acquisition time at somelocations, where the intensity of beam 222 sensed by detector 240 ishigh, and increase the acquisition time at other locations, where theintensity of the sensed X-rays is lower, so as to obtain sufficient, butnot excess, of X-ray photon counting statistics.

In alternative embodiments, processor 22 may apply pre-processing, suchas down-sampling and principal component analysis (PCA), to rawelectrical signals received from detector 240, such as 1D intensityprofiles and/or 2D images for one or more rotation angles. Subsequently,processor 22 may apply one or more machine learning algorithms to thepre-processed data and to complementary data that can be used forassessing the value of the data, such as electrical test data of (e.g.,of the features in question).

In these embodiments, processor 22 may use any suitable types of machinelearning algorithms, such as the TensorFlow open-source machine learningframework initially developed by Google (Mountain View, Calif.), astraining decks for deep learning using neural networks.

Processor 22 may subsequently apply the trained model obtained based ona preceding dataset, to data measured on subsequent wafers 190, so as topredict the electrical performance of the respective device under test,or to provide a user of systems 10, 30 and 40, other useful attributesbased on the data measured on the subsequent wafers 190. Note that usingthe embodiments of such machine learning algorithms may require highsampling so as to develop reliable regression-based models.

In some embodiments, detector 240 comprises electronic circuitries (notshown) configured to discriminate between low-energy and high-energyphotons of beam 220. In some embodiments, processor 22 is configured toreduce the background intensity caused, for example, by X-rayfluorescence and high-energy cosmic rays.

In other embodiments, processor 22 is configured to remove many of thehigh-energy cosmic rays using software-based filters in combination withthe sub-pixel resolution enhancement described above. In theseembodiments, detector 240 may not include the hardware-based cosmic raydiscrimination described above.

Detection of x-Ray Beam Before Impinging on the Sample

It has been found that the intensity of the direct beam passing througha semiconductor wafer in a SAXS system may not be an accurate measure ofthe intensity of the x-ray beam before incident on the semiconductorwafer. Accurate measurement of the incident beam intensity improves thequality of the measurements (such as critical dimensions) of microscopicstructures of a semiconductor sample.

For example—when high aspect ratio (HAR) holes of a semiconductor waferare illuminated at zero (or small) tilt angle then the scattering fromthe HAR holes may be significant. HAR means a ratio between depth andwidth, whereas aspect ratio that exceeds 10:1 is regarded as a highaspect ratio.

In such cases, an estimate of the direct beam intensity can be made byrotating the sample through some known tilt angle and correcting theintensity according to I(omega)=I0*exp[−mu*t/cos(omega)] where mu is thelinear attenuation coefficient of the substrate, normally Si, at theincident X-ray energy and t is the thickness of the substrate. Therotation of the sample require large and complex hardware and is timeconsuming.

Rotating the sample effectively reduces the strength of the scatteredX-rays more strongly than the reduction of the direct beam fromattenuation if the scattering is not negligibly small (say <1%).

There is provided a system, computer program product and a method thatselectively positions a sensor (x-ray intensity detector) in the path ofthe x-ray beam in order to measure the intensity of the x-ray beambefore the x-ray beam reaches the semiconductor sample.

The sensor may be positioned in the path of the x-ray beam during a beamintensity monitoring period and may be positioned outside the path ofthe x-ray beam during a semiconductor sample measurement period. Therelatively weak intensity of the SAXS pattern may require removing thesensor from the path of the x-ray so as not to significantly reduce theintensity of the beam.

The sensor may be inserted in the path of the x-ray beam and may beremoved from said path using any type of movement—linear movement,non-linear movement (such as but not limited to rotational movement) ora combination of a non-linear and linear movements.

The linear movement may be in any direction and the rotational movementmay be about any axis of rotation.

FIGS. 11-14 illustrates various non-limiting examples of rotations. Inthese figures the sensor 702 may be held and moved by a mechanicalmechanism (not shown in some of the figures). The mechanical mechanismmay be an arm attached to an actuator. The sensor 702 may be held and/ormoved by any other holding and/or movement mechanism.

The upper part of FIG. 11 illustrates x-axis movement 715, a y-axismovement 715, a linear movement along an axis 713 that is oriented toboth x-axis and y-axis, and various rotations 711, 714 and 715. Itshould be noted that the rotations are about a support element thatsupports the sensor. Rotating the sensor itself about a center of thesensor may be used only when such a rotation removes the sensor from thepath of the x-ray beam.

FIG. 12 illustrates the sensor 702 outside the path of the x-ray beam(in an “outside location”).

FIG. 13 illustrates various rotations of the sensor 702 to be within thepath x-ray beam (above an aperture or micro slit formed by plates 520movable along blades 510A and 510B movable along respective translationaxes 516A and 516B.

At the upper part of FIG. 13 , the sensor 702 is located above theaperture—and is in a measurement position.

The middle part and the lower part of FIG. 13 illustrates the sensor 702at an outside position and the paths (717 and 718 respectively) betweenthe outside position and the measurement position.

In the middle part of FIG. 13 the sensor 702 is rotated in a plane thatis parallel to the plane of plates 520 while in the lower part of FIG.13 the sensor 702 is rotated in a plane that is normal to the plane ofplates 520.

The rotation can be made in any plane having any spatial relationship tothe plane of plates 520.

The upper and middle parts of FIG. 13 are top views while the bottompart of FIG. 13 is a side view.

FIG. 14-16 illustrates different spatial relationships between (a) thesensor 702 and the actuator 701 and (b) micro-slit assembly 140 thatincludes actuator 600 that moves a blade 550 that includes a series offixed size apertures made using “scatterless pinhole” technology. Thesefigures illustrate various examples of movements that position thesensor 702 in the path (measurement position) and outside the path ofthe x-ray beam (outside position).

FIGS. 15 and 16 also illustrates the path of the x-ray beam when thesensor is removed from the path. When positioned in the path of thex-ray beam (measurement position), the distance between the sensor 702and the closest beam shaping element may be, for example, millimetric (1mm, few millimeters or below 1 mm). Other distances may be used.Similarly, smaller rotation angles to that shown in FIG. 16 may be usedso as to move the sensor 702 away from the beam shaping elements by amillimetric distance to reduce the overall size of the mechanism.

FIGS. 17-18 illustrate system 10 of FIG. 1 which also includes sensor702.

FIGS. 17 and 18 provide examples of the relative position of the sensor702—after the beam is shaped—in the path of the x-ray beam (FIG. 18 )and outside the path of the x-beam (FIG. 17 ).

FIG. 19 illustrates an example of sensor 701 positioned after the beamconditioning assembly 165 of FIG. 4 .

The sensor 702 may be any type of sensor capable of measuring theintensity of the x-ray beam. For example—the sensor may be a siliconsensor, a gallium arsenide sensor, a CdTe sensor, a pin diode, and thelike. The sensor 702 may output an output current or other physicalproperty that is indicative of the intensity of the x-ray beam. Yetaccording to another example—the sensor may be a metal foil that emitsstrong X-ray fluorescence, whereas the intensity of the fluorescentX-rays reflect the intensity of the x-ray beam.

FIG. 20 illustrates a method 905.

Method 905 includes:

-   -   a. Step 915 of measuring an intensity of an x-ray beam by a        sensor that is positioned in a path of the x-ray beam and before        a semiconductor sample. Step 915 occurs during a beam intensity        period. Step 915 may include or may be preceded by positioning        the sensor in the path of the x-ray beam.    -   b. Step 925 of illuminating the semiconductor sample with the        x-ray beam while the sensor is not in the path of the x-ray        beam, and detecting signals (such as a SAXS pattern) from the        semiconductor sample. Step 915 occurs during a semiconductor        sample measurement period. Step 925 may include or may be        preceded by positioning the sensor outside the path of the x-ray        beam.    -   c. Step 935 of processing the signals detected during step 935        to provide an indication about the semiconductor sample—for        example measurements of the semiconductor sample.

Multiple iterations of steps 915, 925 and 935 may be executed.

For example—iterations of these steps may be done several times duringthe measurement of a wafer. For example, after each sample tilt. Theintensity can then be used to normalize the measure data or be includedin a parametric model to scale the intensity to compensate for long-termdrifts due, for example to temperature variations.

It has been found that blocking the direct beam improves the quality ofmeasurements of scattered radiation. When the intensity of the x-raybeam is measured before reaching the semiconductor sample the directbeam may be attenuated and blocked, or partially blocked, by a staticbeam-blocker. This simplifies the system as the beam blocker is notrequired to move between (a) a first position in which it blocks thedirect beam, and (b) a second position in which it does not block thedirect beam or any part of the SAXS pattern.

Any of the apparatuses may not require a beam-blocker, for example whenusing a detector with a highly absorbing sensor such as thick CdTe orGaAs.

In any of the apparatuses the beam blocker may be removed to measure thedirect beam intensity with a short measurement and then inserted tomeasure the scattering from the structures which takes much moretime—thereby protecting the detector from damage by avoiding longexposures with the most intense parts of the beam.

System with XRF Sensor

Semiconductor metrology tools involving more than one X-ray basedanalytical technique are generally known in the art such as Vu et al(U.S. Pat. No. 6,381,303) who combined XRF and XRR and specificallySAXS+XRF combinations are known from Yokhin et al (U.S. Pat. No.7,551,719), Paris et al (2007), or Beckman et al U.S. Pat. No.9,778,213. The apparatus can be used to measure with more than onetechnique either sequentially or simultaneously using one, or more,X-rays beams and detectors. In previous SAXS+XRF tools the detectorshave been comprised of discrete or arrays of X-ray detectors off to theside of the incident X-ray beam such as shown in FIG. 21 (x-ray 131propagates along a certain axis that is normal to sample 190 while theX-ray detector 744 is positioned at one side of the x-ray beam,relatively distant from the sample and oriented at a certain angle).

While this is convenient to implement using off the shelf components,the performance of such systems in terms of measurement precision in agiven time is compromised because of the need to move the detector outof the path of the incoming X-ray beam which limits the possible solidangle of collection.

There may be provided an x-ray fluorescence (XRF) detector within atransmission geometry SAXS tool that addresses the limitations ofperformance due to the limited solid angle of collection of thedetector. The XRF detector may include one or more silicon driftdetectors (SDDs) monolithically manufactured on a single modulecontaining an aperture that allows a beam to pass through.

FIG. 22 illustrates an XRF detector 750 that includes an aperture 7501and one or more SSD that form a single detection region 7502.

FIG. 22 also illustrates an XRF detector 750′ that includes an aperture7501 and one or more SSD that form multiple detection regions 7502A,7502B, 7502C and 7502D.

The number of independent detection regions, the shape and/or size ofthe independent regions may differ from those illustrated in FIG. 22 .

The aperture allows an x-ram beam to pass through the XRF detectorbefore impinging on the sample.

Since the detector is not positioned off to the side of the incidentX-ray beam it can be placed very close to the surface of the sample (1-2mm) and collect a much larger solid angle of fluorescent X-rays emittedfrom a sample.

Quantification of the emitted X-rays can be direct extraction, such ascounting the number of X-ray photons within a specific energy region ofinterest (ROI) or from fitting in order to separate overlapping peaks.

Such a setup can be used in two main ways within a combined transmissionSAXS and XRF tool as disclosed below:

-   -   1) Placed near (for example at a distance smaller than 5 mm        from) the backside of a wafer to measure the fluorescent X-rays        such as Si Ka radiation from Si wafers in order to monitor the        intensity of the incident beam with increased precision than        setups known in the prior art    -   2) Placed near (for example at a distance smaller than 5 mm        from) the front-side of the wafer to measure the X-rays emitted        from structures patterned on or within the substrate such as        logic or memory structures, including but not limited to FinFETs        and gate-all around (GAA) transistors, DRAM, NAND or novel        technologies such as phase change or magnetic memories. The XRF        and SAXS signals can be measured sequentially or simultaneously        and the uXRF signal can be used in a number of ways including        independent use to monitor the volume of a material within        structures containing W metal to quantify and monitor voiding.

In both setups the XRF detector is sufficiently small so that it can(optionally) rotate with the sample if needed to maintain closeproximity with the surface of the sample. An example of such a detectorby means of example is the Rococo series manufactured by PNDetector(Munich, Germany).

Since the X-ray beam in a transmission SAXS system has a relatively highenergy typically greater than 15 keV then only relatively high Zmaterials such as W can be excited by this incident X-ray beam.Therefore, in another embodiment it is envisaged that a second X-raybeam may be incident on the front size of the sample with a differentenergy from that of the SAXS X-ray beam. The properties of this beamincluding energy, size and angular divergence may be different to theSAXS beam and separately optimized to excite fluoresce from elementsthat are not efficiently excited by the SAXS beam. Possible excitationsinclude, but are not limited to, X-ray emissions from common X-ray tubessuch as Cu, Rh, Mo.

FIGS. 23 and 24 illustrate XRF detector 750 positioned upstream tosample 190 and allowing x-ray 130 to pass through XRF detector 750 andimpinge on sample 190. In FIG. 23 the x-ray is normal to sample 190 andto the XRF detector 750, while in FIG. 24 the x-ray is not normal to thesample and the XRF detector 750.

The XRF detector is small and so close to the sample 190 that it mayrotate with the sample.

The proximity of the XRF detector to the sample 190 and the apertureallowing the x-ray to pass therethrough enable the XRF detector tocollect fluorescent x-rays emitted over a large solid angle range. Thelarge solid angle range may exceed 0.5 sr, may be about 1 sr, or mayexceed 1 sr.

FIG. 25 illustrates an example of a sample 190, x-ray beam 130 and XRFdetector 750 (having aperture 7501) and a second x-ray beam 132 thatilluminates the second side of the sample 190 (while passing throughaperture 7501). In this case the XRF detector 750 may detect fluorescentx-rays emitted from structure on or within the second side of the sample190. The second x-ray beam 132 may be optimized to excite X-rayfluorescence of certain elements of interest.

FIGS. 26 and 27 illustrates system 10 with XRF detector 750 positionedupstream to the sample 190—at different sample tilt angles.

FIG. 28 illustrates system 10 with XRF detector 750 positioneddownstream to the sample 190 and having a second x-ray 132 illuminatethe sample though an aperture of XRF detector 750.

FIGS. 29 and 30 illustrates system 10 with detector 702 (x-ray intensitydetector) located upstream to the sample and XRF detector 750 positioneddownstream to the sample 190, and having a second x-ray beam 130′illuminate the sample though an aperture of XRF detector 750. In FIG. 29the detector 702 is located at an outside position and in FIG. 30 thedetector 702 is in a measurement position.

Detecting the entirety of the x-ray beam may be more accurate thansampling a part of the x-ray beam.

FIG. 31 illustrates method 1200.

Method 1200 may include steps 1210, 1220, 1230, 1240, 1250 and 1260.

Step 1210 may include holding a sample by a mount.

Step 1220 may include directing an x-ray beam toward a first side of thesample.

Step 1210 may include or may be followed by positioning the XRF detectorwithin less than five millimeters from the first side of the sample.

Step 1210 may include or may be followed by positioning the XRF sensordownstream to the second side of the sample.

Step 1230 may include detecting, by a small angle x-ray scattering(SAXS) detector that is positioned downstream to a second side of thesample, at least a part of a SAXS pattern formed by x-rays that havebeen transmitted through the sample and exited through the second side.

Step 1210 may include or may be followed by positioning the XRF sensordownstream to the second side, wherein step 1230 may include detectingthe at least part of the SAXS pattern that passes through the apertureof the XRF sensor.

It should be noted that the XRF sensor may be moved by a movementmechanism between a measurement position (in which it performs an XRFmeasurement) and an outside position.

Step 1240 may include detecting, by an x-ray fluorescence (XRF)detector, fluorescent x-rays emitted from the sample.

Step 1250 may include responding to the detection. The responding mayinclude evaluating the sample, evaluating an x-ray beam property, andthe like.

Method 1200 may also include positioning the XRF upstream to the sampleand determining an intensity of the x-ray beam based on the fluorescentx-rays that were detected by the XRF detector.

The XRF detector may include an aperture. The x-ray beam may passthrough the aperture.

The XRF sensor may be positioned upstream to the first side of thesample.

Step 1220 may include directing the x-ray to pass through the aperture.

Method 1200 may also include positioning the XRF downstream to thesample (for example facing the second side of the sample) andilluminating the sample with another x-ray beam (1260) that may passthrough the aperture of the XRF sensor. Step 1260 may be followed bystep 1220.

The sample may be illuminated by the x-ray beam and the other x-ray beamconcurrently, during different points of time or during partiallyoverlapping periods of time.

The XRF detector may be shaped and positioned to detect fluorescentx-rays emitted from the sample over a large solid angle range. The largesolid angle range may exceed 0.5 sr, may be about 1 sr, or may exceed 1sr.

Step 1240 may be including detecting, by one or more radiation sensingelements of the XRF detector, fluorescent x-rays emitted from thesample.

Determining Orientations of HAR Holes

There may be provided a method for determining the orientation of HARholes of an array of stacks of HAR holes. The determining may includegenerating orientation information that is indicative of the orientationof HAR holes of an array of stacks of HAR holes.

It is assumed that the array includes substantially identical stacks ofHAR holes—and that a small-angle X-ray scattering (SAXS) patternobtained by illuminating the array is indicative of the orientation ofHAR holes of each stack.

The method may include determining the orientation of one or more HARholes of a stack in relation to a surface of the wafer. The method mayinclude determining the misalignment between HAR holes of the stack.

The lower part of FIG. 32 illustrates an array of aligned stacks 800 ofHAR holes. The upper part of FIG. 32 illustrates an array of misaligned800′ stacks of HAR holes.

The left side of FIG. 33 illustrates an aligned stack 800 that includesa first HAR hole 801 and a second HAR hole 802.

First HAR hole 801 is formed in a first layer 812 of a wafer.

Second HAR hole 802 is formed in a second layer 814 of a wafer.

The upper surface of first layer 812 is denoted 811. The bottom surfaceof the second layer 814 is denoted 818. The lower surface of first layer812 and the upper surface of the second layer are denoted 813.

Both HAR holes are mutually aligned and are perpendicular to the uppersurface 811 of first layer 812 of the wafer.

The right side of FIG. 33 illustrates a misaligned stack 800′ thatincludes a first HAR hole 801 and a second HAR hole 802. Both holes arenot perpendicular to the upper surface 811 of first layer 812 and arealso mutually misaligned (by misalignment angle MA 823).

First HAR hole 801 is oriented by first angle OR1 821 in relation tonormal 819. Second HAR hole 802 is oriented by second angle OR2 822 inrelation to normal 819. In this example OR1 differs from OR2.

The bottom of FIG. 33 illustrates a misaligned stack 800″ that includesa first HAR hole 801 and a second HAR hole 802. Both HAR holes are notperpendicular to the upper surface 811 of first layer 812 and are alsomutually misaligned. First HAR hole 801 is oriented by first angle OR1821 in relation to normal 819. Second HAR hole 802 is oriented by secondangle OR2 822 in relation to normal 819. In this example OR1 differsfrom OR2. The bottom of FIG. 32 also illustrates a straight pass-throughpath 818 that passes straight through both holes. Path 818 is orientedby OR3 824 from normal 819.

It should be noted that one HAR hole may be normal to the first surfacewhile another HAR hole may be oriented in relation to normal 819. Yetfor another example—one HAR hole of the stack may be spatially offsetfrom another HAR hole of the stack—have center of one HAR hole spacedapart from a center of another HAR hole of the stack.

It should be noted that each stack may include more than two HAR holes.

FIG. 34 illustrates a SAXS pattern 1600 that represents the intensity ofradiation versus collection angles of a sensor. The center of the SAXSpattern corresponds to a zero collection angle.

One or more angular ranges of the pattern are defined. The one or moreangular ranges may be defined in any manner and/or by any entity.

The one or more angular ranges may be fixed, may change over time, maybe defined using machine learning, or may be defined in any othermanner. The angular ranges may be selected in order to provideorientation information.

Different SAXS patterns are obtained for different angular relationshipsbetween the array and the illuminating X-ray. The different angularrelationships may be obtained by rotating the array and/or by rotatingthe X-ray about a rotation axis.

FIG. 53 illustrates an example of a 2D small-angle X-ray scattering(SAXS) pattern obtained when illuminating an array of two levels of HARholes showing the interference pattern due to in-plane spatial shiftsbetween the top and bottom levels of holes. The shift values in the xand y directions are denoted X JS and Y JS, respectively.

The method may include calculating, for each one of the different SAXSpatterns—sum of intensities within each of the one or more angularranges.

The method may also include calculating one or more relationships(angle-intensity sum relationships) between (ii) one or more sums ofintensities related of one or more angular ranges of the different SAXSpatterns (related to different angular relationships), and (ii) thedifferent angular relationships between the illuminating x-ray and thesample.

These one or more angle-intensity sum relationships may be processed inorder to provide the orientation and n-plane shift information.

The strength of the X-ray scattering is proportional to the electrondensity difference of the scattering structures with respect to theirsurrounding environment. Accordingly—the sum of relationships may have afirst peak that corresponds to the orientation of the first HAR hole,and a second peak that corresponds to the orientation of the second HARhole.

There may be a third peak (not shown—located between the first andsecond peaks) that represents a passage of the x-ray via the straightpass-through path.

It should be noted that in some cases different peaks may be merged (forexample—when the peaks are not distant enough from each other).

The processing of the angle-intensity sum relationships may includecomparing an angle-intensity sum relationship to one or more referenceangle-intensity sum relationships (of known stacks of HAR holes), mayinclude applying neural network/deep learning/machine learning on theangle-intensity sum relationships to provide the orientation and/orspatial shift information or extracting the orientation information fromthe angle-intensity sum relationships in any other manner. Theprocessing may include physical modelling with limited subset of tiltangles not just different peaks but also interference patterns at thetwo arrays of holes are illuminated coherently.

Angle-intensity sum relationships of different arrays may be compared toeach other.

FIG. 35 illustrates (from top to bottom) three angle-intensity sumrelationships:

First angle-intensity sum relationship 1611—obtained for an alignedstack—and for first angular range 1601.

Second angle-intensity sum relationship 1612—obtained for an alignedstack—and for second angular range 1602.

Third angle-intensity sum relationship 1613—obtained for an alignedstack—and for third angular range 1603.

FIG. 36 illustrates (from top to bottom) three angle-intensity sumrelationships:

Fourth angle-intensity sum relationship 1621—obtained for a misalignedstack (without a straight pass-through path)—and for first angular range1601.

Fifth angle-intensity sum relationship 1622—obtained for a misalignedstack (without a straight pass-through path)—and for second angularrange 1602.

Sixth angle-intensity sum relationship 1623—obtained for a misalignedstack (without a straight pass-through path)—and for third angular range1603.

The fifth and sixth angle-intensity sum relationships include twodistinct peaks—and thus convey more orientation information that thefourth angle-intensity sum relationship.

FIG. 37 illustrates two angle-intensity sum relationships:

-   -   Seventh angle-intensity sum relationship 1631—obtained for an        aligned stack—and for first angular range 1601.    -   Eighth angle-intensity sum relationship 1632—obtained for a        misaligned stack (without a straight pass-through path)—and for        first angular range 1601.

Both seventh and eighth angle-intensity sum relationships have a singlepeak—but differ from each other—and may provide an indication whetherthe stack is aligned or misaligned.

More detailed orientation information may be obtained from the seventhand eighth angle-intensity sum relationships by further processing—forexample—comparing these angle-intensity sum relationships to referenceangle-intensity sum relationships of known stacks.

The orientation information may be obtained from may include physicalmodelling with limited subset of tilt angles not just different peaksbut also interference patterns at the two arrays of holes areilluminated coherently.

FIG. 38 illustrates method 1700.

Method 18 may include steps 1710, 1720, 1730 and 1740. Step 1710 isfollowed by step 1720. Step 1720 is followed by step 1730. Step 1730 isfollowed by step 1740.

Step 1710 of obtaining different SAXS patterns for different angularrelationships between the wafer and the illuminating X-ray. Thedifferent angular relationships may be obtained by rotating the arrayand/or by rotating the X-ray about a rotation axis.

Step 1720 of calculating, for each one of the different SAXS patterns,sum of intensities within each of the one or more angular range arecalculated.

Step 1730 of calculating one or more relationships (angle-intensity sumrelationships) between (i) one or more sums of intensities related ofone or more angular ranges of the different SAXS patterns (related todifferent angular relationships) and (ii) the different angularrelationships between the illuminating x-ray and the sample.

Step 1740 of processing the one or more angle-intensity sumrelationships to provide the orientation information.

Method 1700 may be executed by the apparatus that obtained the SAXSpatterns or may be calculated by a computer that does not belong to saidapparatus.

Extracting Information Related to an Array of HAR Holes.

There may be provided an apparatus, method and computer program productfor extracting information about the array of HAR holes.

There may be provided an apparatus, method and computer program productthat may substantially remove from the SAXS pattern the contribution ofthe scattering of the x-ray beam by other structures that differ fromthe array of HAR holes (the other structures may be, for example,structures that have vastly different pitches from the HAR holes of theHAR array, structures that may have vastly different heights than theHAR holes of the array, the other structures may form be non-repetitivestructures, may be one or more additional repetitive structures)—so thatthe SAXS pattern is more representative of the scattering by the arrayof HAR holes. For simplicity of explanation it is assumed that theseother structures are one or more additional repetitive structures. HARholes are non-limiting example of HAR structures.

The method may be used to substantially remove from the SAXS patternother noises—such as but not limited to scattering from electronics ofthe detector that are positioned behind the active region. At least apart of the scattered pattern that reaches the active region passesthrough the active region, reaches the electronics, and may be backscattered (by the electronics) towards the active region.

The scattering from the electronics is merely a non-limiting example ofnoise that can be removed from the SAXS pattern. Such scattering may beinsignificant, and the method, system and computer program product canbe applied mutatis mutandis to other noises and/or may be applied evenwhen such scattering is insignificant.

There may be provided an apparatus, method and computer program productthat may analyze complex structures (such as HAR holes) by treatingother scattering elements of the semiconductor sample (such as the oneor more additional repetitive structures) as a source of “background”radiation. In the simplified model the intensity is assumed to be anincoherent sum of the intensity from the HAR holes and the intensityfrom one or more additional repetitive structures (referred to asunderlayers), i.e.I_total(q)=I_HAR(q)+I_underlayers(q)+I_system(q)=I_HAR(q)+I_effectiveBackground(q)

The analysis of the HAR holes may require a reliable model (may not bepossible due to complexity of underlayers or just unknown) or anestimate of I_underlayers(q)+I_system(q)

In order to estimate this “background” intensity distribution a relativetilt may be introduced between the x-ray beam and the semiconductorsample (for example by rotating the semiconductor sample about anomega-axis) so that it is sufficiently high that I_HAR(q)˜0 which istypically somewhere in the range of 5-10 deg (not a hard range but anexample).

These data are then either used directly or fitted using non-linearregression to give a parametric model involving peak functions such asencountered in X-ray analysis, for example sum of Gaussian, Lorentzian,Pseudo-Voigt or Pearson-VIL. Directly using an empirical background maybe advantageous when it cannot be modelled well using common peakfunctions which can, for example be the case for scattered intensityfrom slits in the system.

Once the parameters of this “effective background” mode are determinedthen they are held constant, or varied only slightly, and the intensitycontribution is added to I_HAR(q) at low tilt angles so as to model thetotal scattered intensity distribution.

By accounting for the intensity from the underlayers then we get moreaccurate results for the HAR hole analysis.

FIG. 39 illustrates method 1900.

Method 1900 may start by step 1910 of introducing a first angularrelationship between a semiconductor element and an x-ray beam.

Step 1910 may be followed by step 1920 of illuminating the semiconductorobject with the x-ray beam, while the first angular relationship ismaintained and detecting a first SAXS pattern by a sensor.

While the first spatial relationship is maintained the x-ray beam(before impinging on the semiconductor element) is aligned (orsubstantially aligned) with the HAR holes and is normal (orsubstantially normal) to the longitudinal axis of the one or moreadditional repetitive structures.

While the first spatial relationship is maintained the sensor senses afirst SAXS pattern that has a backscattered radiation component (backscattered from the electronics), and also includes a scattered patternthat is highly affected by the array of the HAR holes, and by the one ormore additional repetitive structures.

Step 1920 may be followed by step 1930 of introducing a second angularrelationship between the semiconductor element and the x-ray beam.

Step 1930 may be followed by step 1940 of illuminating the semiconductorobject with the x-ray beam, while the second angular relationship ismaintained, and detecting a second SAXS pattern the sensor.

While the second spatial relationship is maintained the x-ray beam(before impinging on the semiconductor element) is misaligned (orsubstantially aligned) with the HAR holes and is oblique (orsubstantially oblique) to the longitudinal axis of the one or moreadditional repetitive structures.

While the second angular relationship is maintained second spatialrelationship is maintained the sensor senses a second SAXS pattern thathas a backscattered radiation component (back scattered from theelectronics), and also includes a scattered pattern that is still highlyaffected by the one or more additional repetitive structures but is lessaffected by the array of the HAR holes.

Step 1940 is followed by step 1950 of comparing between the first SAXSpattern and the second SAXS pattern to generate information about thearray of HAR holes.

Especially—step 1950 may include subtracting the first SAXS pattern fromthe second SAXS pattern to provide a SAXS pattern that represents thescattering of the x-ray beam by the array of HAR holes.

The changing of the angular relationship may be executed by rotating atleast one out of the x-ray beam and the semiconductor object.

The maintaining of the first spatial relationship may be associated witha first angular range between the x-ray beam and the semiconductorobject. It has been found that when the aspect ratio of the HAR holesexceeds 10:1 (for example may be 40:1) the first angular range may rangebetween plus two degrees and minus two degrees from a perfect alignment.

The maintaining of the second spatial relationship may be associatedwith a second angular range between the x-ray beam and the semiconductorobject. It has been found that when the aspect ratio of the HAR holesexceeds 10:1 (for example may be 40:1) the second angular range mayinclude deviations of at least two or three degrees from perfectalignment.

Alternatively or additionally, the method may include translating thesample to part of the sample that does not contain the HAR holes such asa scribe line test pad and obtaining an additional SAXS pattern that isless affected by the array of the HAR holes.

The second SAXS pattern and/or the additional SAXS pattern can be usedto provide a SAXS pattern that can be a background SAXS pattern that canbe used (with the first SAXS pattern) to isolate the contribution of thearray of HAR holes to the SAXS pattern.

FIG. 40 illustrates an example of sample such as a semiconductor object.

The semiconductor object includes an array of HAR holes 1882 and one ormore additional repetitive structures such as transistors 1884(2) andinterconnects 1884(1). The HAR holes 1882 may be positioned betweenmultiple layers within a vertical NAND (or 3D NAND) memory array.

The aspect ratio of the structural elements that form the one or moreadditional repetitive structures is much smaller than the aspect ratioof the HAR holes. These structural elements may be much thinner (alongthe x-axis) than the HAR holes. Accordingly—the scattering attributed tothe HAR holes is much more sensitive to rotation that the scatteringattributed to the one or more additional repetitive structures.

FIG. 41 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus. In this figure the first angularrelationship is maintained between x-ray 1852 and semiconductor object1880.

In FIG. 41 the HAR holes 1882 and the one or more additional repetitivestructures (collectively denoted 1884) scatter the x-ray to provide ascattered pattern that is generated due to scattering of the x-ray beamby the array of the HAR holes, and by the one or more additionalrepetitive structures.

The sensor 1820 has an active region 1822 and electronics 1824. Theelectronics backscatter radiation to provide backscattered radiation1856.

The sensor 1820 senses a first SAXS pattern that has a backscatteredradiation component (back scattered from the electronics), and alsoincludes a scattered pattern that is generated due to scattering of thex-ray beam by the array of the HAR holes, and by the one or moreadditional repetitive structures.

FIG. 42 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus. In this figure the second angularrelationship is maintained between x-ray 1852 and semiconductor object1880.

In FIG. 42 the HAR holes 1882 almost to not affect the second SAXSpattern while the one or more additional repetitive structures(collectively denoted 1884) scatter the x-ray to provide a scatteredpattern 1854 that is generated due to scattering of the x-ray beam bythe one or more additional repetitive structures.

The electronics 1824 backscatter radiation to provide backscatteredradiation 1856.

The sensor 1820 senses a second SAXS pattern that has a backscatteredradiation component (back scattered from the electronics), and alsoincludes a scattered pattern that is generated due to scattering of thex-ray beam by one or more additional repetitive structures.

Evaluating an Object from Different Angles

There may be provided an apparatus, method and computer program productfor inspecting a semiconductor object from different angles.

The semiconductor object includes an array of structural elements. Thesestructural elements have an electron density that substantially differsfrom the electron density of their surroundings. These structuralelements have a longitudinal axis of a certain direction, and exhibit ahigh aspect ratio (HAR).

Non-limiting example of the structural elements are HAR holes—eitherfilled HAR holes or unfilled HAR holes. It is noted that the structuralelements may differ from HAR holes. For simplicity of explanation it isassumed that the structural elements are HAR holes.

The most intense scattering (strongest SAXS pattern) occurs when theX-rays are aligned with structure is because this is the direction thatminimizes the net path, and hence, phase differences between the objectsin the array and hence minimizes the reduction in intensity fromdestructive interference. In this “forward” direction there are thehighest number of diffraction peaks visible because of the highintensity and it may be beneficial to obtain good angular resolution intwo directions—both along the x-axis and the y-axis.

Angular deviation from this setup (before hitting the semiconductorobject) provides lower quality SAXS patterns.

According to an embodiment of the invention there may be provided amethod that determines one or more x-ray beam parameters (such as x-raybeam shape and/or size) as a function of the angular relationshipbetween the x-ray beam and the semiconductor object.

For example—when the x-ray beam is aligned (before hitting thesemiconductor object) with the HAR holes (assuming that the sensor andthe semiconductor object are parallel to each other)—the x-ray beam maybe collimated in both x-axis and in y-axis. This will result, forexample, of a circular cross section of the x-ray beam at the plane ofthe sensor, at the plane of the semiconductor object and at the outputof the x-ray source—for example at a plane of micro-slits that shape thecross section of the beam.

The suggested system and method may change the range of anglesilluminating the sample without changing the area of illumination (onthe sample). At a certain spatial relationship there may be a low rangeof incident angles (collimated beam) in the vicinity of the beam beingnormal to the features/sample and at another spatial relationship (forexample a larger tilt) the angular range may be increased. In both casesthe spot (on the sample) may be maintained at a relatively smallarea—for example by focusing the x-ray beam on the spot. Slits(apertures) are positioned before the optics and before the sampletowards the source may be increased to increase the range of angles.Additionally, the suggested system and method may change the area ofillumination without changing the range of angles illuminating thesample by changing the sizes of the aperture of the slits before theoptic and before the sample.

Assuming that the semiconductor object is rotated in relation to thedetector and to the x-ray beam then the x-ray beam may be collimatedalong the x-axis while be non-collimated along the y-axis at the planeof the sensor and at the output of the x-ray source—and have anelliptical shape. At the plane of the semiconductor object the x-raybeam is circular.

The eccentricity of the ellipse changes with the angular misalignment.

Larger range of incident angles may increase the strength of the SAXSpatterns—but may increase the overlap between diffraction orders of theSAXS patterns. The overlaps as the tilt angle is increased may betolerated and beneficial—at is may be compensated by using SAXS patternsthat were acquire using less overlapping or even non-overlapping SAXSpatterns—obtained at lower angular misalignments.

A gain in intensity may be beneficial over the loss in angularresolution for higher tilt angles since there are fewer diffractionpeaks and they have relatively low intensity compared to case of lowtilt angles of the sample.

The change in the range of angular illumination at the sample may beperformed in various manners—for by using an aperture of an adjustableshape and/or size, by selecting between apertures that differ from eachother by shape and/or size, by using different reflective and/ordiffractive optics optimized for collimated and focused beams and thelike.

The parameters of the x-ray beam (for example a size and/or eccentricityof an elliptical cross section of the x-ray beam) may be a set based onat least one out of:

The deviation angle between the x-ray beam and a certain direction inwhich the HAR holes and the x-ray beam are aligned. For example, thesize of the beam may be reduced as the angle of the sample is increasedso as to maintain a constant illuminated area on the sample, which canbe important for small test pad structures. Also, the divergence of theX-ray beam may be reduced (increased resolution) when the X-ray beam issubstantially parallel to the axis of the HAR holes so as to clearlyresolve the individual diffraction orders and increase the sensitivityto disorder within the array that is not accessible with higherdivergences used to assess the average shape of the HAR holes. As anexample, for HAR holes with an in-plane spacing of ˜150 nm then atypical high-resolution divergence may be ˜0.2 mrad whereas a high-fluxdivergence used to assess average shape may be around 0.4-0.5 mrad.

Any measured and/or estimated parameter of the sensed SAXS pattern (suchas but not limited to a measured and/or estimated SNR of the SAXSpattern). For example, the divergence angle of the X-ray beam may beadjusted in one direction to increase the incident flux substantiallyand accuracy/precision or throughput when measuring 2D structures, suchas HAR trenches, that do not require high resolution in both directionsin the plane of the sample in order to determine the shape of thestructure.

The expected overlap between different lobes of the SAXS pattern dependson the pitch of the structure relative to the divergence of the incidentX-ray beam with smaller pitch structures having larger spacing betweenadjacent diffraction orders and, as such, can benefit from a higherdivergence beam with higher flux than a large pitch structure. Forexample, scattering from dynamic random-access memory (DRAM) capacitorstructures with pitch <100 nm can be advantageously measured with ahigher divergence (>0.5 mrad for example) beam for 3D NAND channel holeswith pitch ˜150 nm where a divergence >0.5 mrad would cause significantoverlap between adjacent diffraction orders which would degrade theaccuracy and precision of the profile from the later structures.

Information already obtained in previous measurements—especially whenone or more different angular relationships existed between the x-raybeam and the semiconductor object during the previous measurements.information

The importance and/or priority of structures of the semiconductor objector the relevance of information that may exist in overlap areas betweenlobes of the SAXS pattern. For example, in the case of a vertical stackof two arrays of HAR holes then the information concerning the in-planeoffset between the arrays can be determined using a beam with increaseddivergence and higher flux and at higher throughput than if accurateshapes of the holes is required due to the rather low frequency of theinterference pattern as compared to the spacing between adjacentdiffraction orders (see FIG. 53 ).

It should be noted that the shape of the x-ray beam may be elliptical ornon-elliptical, may be a polygon, a curved shape, and the like.

It should be noted that the x-ray beam energy density may be changedfrom one measurement to another.

FIG. 43 illustrates method 1000.

Method 1000 may start by step 1010 of receiving or determiningparameters (such as but not limited to at least one out of intensity,divergence, shape and size) of an x-ray beam and determining an angularrelationship between a semiconductor element and the x-ray beam.

Step 1010 may be followed by step 1020 of introducing the angularrelationship between the semiconductor element and the x-ray beam.

Step 1020 may be followed by step 1030 of illuminating the semiconductorobject by an x-ray beam that has the parameters, while the angularrelationship is maintained, and detecting a SAXS pattern (or any othersignal) by a sensor.

Step 1030 maybe followed by step 1010—during which the method may changeat least one out of (a) one or more parameters of the x-ray beam, and(b) the angular relationship.

Multiple iterations of steps 1010-1030 may be executed.

The determining of step 1010 may be responsive to an outcome of step1030. For example—a SAXS pattern (or any other signal) may be processedand/or analyzed to determine one or more parameters of the SAXS pattern(or any other signal).

Step 1010 may include determining the parameters of the x-ray beam (forexample a size and/or eccentricity of an elliptical cross section) basedon at least one out of:

-   -   a. The deviation angle.    -   b. Any measured and/or estimated parameter of the sensed SAXS        pattern (such as but not limited to a measured and/or estimated        SNR of the SAXS pattern).    -   c. The expected overlap between different lobes of the SAXS        pattern.    -   d. Information already obtained in previous measurements—when        one or more different angular relationships existed between the        x-ray beam and the semiconductor object.    -   e. The importance and/or priority of structures of the        semiconductor object.    -   f. The relevance of information that may exist in overlap areas        between lobes of the SAXS pattern.

For example—

The deviation angle between the x-ray beam and a certain direction inwhich the HAR holes and the x-ray beam are aligned. For example, thesize of the beam may be reduced as the angle of the sample is increasedso as to maintain a constant illuminated area on the sample, which canbe important for small test pad structures. Also, the divergence of theX-ray beam may be reduced (increased resolution) when the X-ray beam issubstantially parallel to the axis of the HAR holes so as to clearlyresolve the individual diffraction orders and increase the sensitivityto disorder within the array that is not accessible with higherdivergences used to assess the average shape of the HAR holes. As anexample, for HAR holes with an in-plane spacing of ˜150 nm then atypical high-resolution divergence may be ˜0.2 mrad whereas a high-fluxdivergence used to assess average shape may be around 0.4-0.5 mrad.

Any measured and/or estimated parameter of the sensed SAXS pattern (suchas but not limited to a measured and/or estimated SNR of the SAXSpattern). For example, the divergence angle of the X-ray beam may beadjusted in one direction to increase the incident flux substantiallyand accuracy/precision or throughput when measuring 2D structures, suchas HAR trenches, that do not require high resolution in both directionsin the plane of the sample in order to determine the shape of thestructure.

The expected overlap between different lobes of the SAXS pattern dependson the pitch of the structure relative to the divergence of the incidentX-ray beam with smaller pitch structures having larger spacing betweenadjacent diffraction orders and, as such, can benefit from a higherdivergence beam with higher flux than a large pitch structure. Forexample, scattering from dynamic random-access memory (DRAM) capacitorstructures with pitch <100 nm can be advantageously measured with ahigher divergence (>0.5 mrad for example) beam for 3D NAND channel holeswith pitch ˜150 nm where a divergence >0.5 mrad would cause significantoverlap between adjacent diffraction orders which would degrade theaccuracy and precision of the profile from the later structures.

Information already obtained in previous measurements—especially whenone or more different angular relationships existed between the x-raybeam and the semiconductor object during the previous measurements.information

The importance and/or priority of structures of the semiconductor objector the relevance of information that may exist in overlap areas betweenlobes of the SAXS pattern. For example, in the case of a vertical stackof two arrays of HAR holes then the information concerning the in-planeoffset between the arrays can be determined using a beam with increaseddivergence and higher flux and at higher throughput than if accurateshapes of the holes is required due to the rather low frequency of theinterference pattern as compared to the spacing between adjacentdiffraction orders (see FIG. 53 ).

It should be noted that during one of more iteration of steps 1010-1030the semiconductor object may be illuminated with an x-ray propagates atthe certain direction.

FIG. 44 illustrates an example of a semiconductor object.

The semiconductor object includes an array of HAR holes 1882. The HARholes may be positioned between multiple layers within a vertical NAND(or 3D NAND) memory array or test structure.

FIG. 45 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus. In this figure the first angularrelationship is maintained between x-ray 1852 and semiconductor object1880.

In FIG. 45 the HAR holes 1882 scatter the x-ray to provide a scatteredpattern 854 that is generated due to scattering of the x-ray beam by thearray of the HAR holes.

FIG. 46 illustrates an example of semiconductor object and of some partsof an X-ray scatterometry apparatus. In this figure the second angularrelationship is maintained between x-ray 1852 and semiconductor object1880.

FIGS. 47-52 illustrates cross sections of the x-ray beam at (a) theplane 140′ of micro-slits 140, (b) the plane 190′ of semiconductorobject 190, and (c) at the plane 124′ of the sensor 140.

FIGS. 47-50 illustrate four example of four angularrelationships—starting from alignment (FIG. 47 —circular cross sections1011, 1021 and 1031—at three planes 124′, 190′ and 140′), and continuingwith elliptical cross sections of growing eccentricity (corresponding toincreased misalignment)—in FIGS. 48, 49 and 50 (elliptical crosssections 1012, 1013 and 1014 at plane 124′, elliptical cross sections1032, 1033 and 1034 at plane 140′) and circular cross section 1022; 1023and 1024 at semiconductor plane 190′.

FIG. 51 illustrates a non-overlapping SAXS pattern 1041 obtained whenthe incident beam is aligned with the HAR holes and also illustrates anoverlapping SAXS pattern 1042 obtained when the incident beam ismisaligned with the HAR holes.

FIG. 52 illustrates a SAXS pattern 1043 that is obtained in the case ofhigher tile—which illustrates a higher divergence and less intensity.

There may be provided an x-ray apparatus that may include a mount thatmay be configured to hold a sample; an x-ray source, that may beconfigured to direct an x-ray beam toward a first side of the sample; adetector, positioned downstream to a second side of the sample, thedetector may be configured to detect, during a sample measurementperiod, at least a part of x-rays that have been transmitted through thesample; and an x-ray intensity detector that may be positioned, during abeam intensity monitoring period at a measurement position that may belocated between the x-ray source and the first side of the sample, so asto detect at least a part of the x-ray beam before the x-ray beamreaches the sample.

The sample measurement period and the beam intensity monitoring perioddo not overlap.

When positioned at the measurement position, the x-ray intensitydetector may be configured to receive an entirety of the x-ray beam.

The x-ray apparatus may include a mechanical mechanism that may beconfigured to move the x-ray intensity detector between (a) themeasurement position, and (b) an outside position in which the x-rayintensity detector may be positioned outside a path of the x-ray beam.

The mechanical mechanism may be configured to move the x-ray intensitydetector between the measurement position and the outside position by arotational movement within a plane that may be parallel to a plane ofthe first side of the sample.

The mechanical mechanism may be configured to move the x-ray intensitydetector between the measurement position and the outside position by arotational movement within a plane that may be not parallel to a planeof the first side of the sample.

The mechanical mechanism may be configured to move the x-ray intensitydetector between the measurement position and the outside position by alinear movement within a plane that may be parallel to a plane of thefirst side of the sample.

The mechanical mechanism may be configured to move the x-ray intensitydetector between the measurement position and the outside position bylinear movements within a plane that may be not parallel to a plane ofthe first side of the sample.

The x-ray apparatus may include a beam limiter positioned upstream tothe measurement position, wherein the beam limiter may include at leastone mechanical element configured to determine at least one of a shapeof the x-ray beam and a size of a cross section of the x-ray beam.

The mechanical mechanism may be configured to move the x-ray intensitydetector between the measurement position and the outside position by amovement that may be parallel to the at least one mechanical element.

The mechanical mechanism may be configured to move the x-ray intensitydetector between the measurement position and the outside position by amovement that may be non-parallel to the at least one mechanicalelement.

The beam limiter may include first and second blades, having respectivefirst and second edges positioned in mutual proximity so as to define aslit, through which the beam of the X-rays will pass, at a distancesmaller than mm from the first side of the sample; and first and secondactuators, which may be configured to shift the first and second bladesalong respective, first and second translation axes so as to adjust awidth of the slit.

The sample measurement period and the beam intensity monitoring periodpartially overlap.

The x-ray apparatus may be a semiconductor metrology tool.

There may be provided a method that may include holding a sample by amount;

directing an x-ray beam toward a first side of the sample; detecting,during a sample measurement period and by a detector positioneddownstream to a second side of the sample, at least a part of x-raysthat have been transmitted through the sample and exited through thesecond side; and detecting at least a part of the x-ray beam before thex-ray beam reaches the sample, during a beam intensity monitoring periodand by an x-ray intensity detector positioned at a measurement positionthat may be located between the x-ray source and the first side of thesample.

The sample measurement period and the beam intensity monitoring perioddo not overlap.

When positioned at the measurement position, the x-ray intensitydetector may be configured to receive an entirety of the x-ray beam.

The method may include a mechanical mechanism that may be configured tomove the x-ray intensity detector between (a) the measurement position,and (b) an outside position in which the x-ray intensity detector may bepositioned outside a path of the x-ray beam.

The method may include moving the x-ray intensity detector between themeasurement position and the outside position by a rotational movementwithin a plane that may be parallel to a plane of the first side of thesample.

The method may include moving the x-ray intensity detector between themeasurement position and the outside position by a rotational movementwithin a plane that may be not parallel to a plane of the first side ofthe sample.

The method may include moving the x-ray intensity detector between themeasurement position and the outside position by a linear movementwithin a plane that may be parallel to a plane of the first side of thesample.

The method may include moving the x-ray intensity detector between themeasurement position and the outside position by a linear movementwithin a plane that may be not parallel to a plane of the first side ofthe sample.

The method may include determining, by a beam limiter positionedupstream to the measurement position and may include at least onemechanical element, at least one of a shape of the x-ray beam and a sizeof a cross section of the x-ray beam.

The method may include moving the x-ray intensity detector between themeasurement position and the outside position by a movement that may beparallel to the at least one mechanical element.

The method may include moving the x-ray intensity detector between themeasurement position and the outside position by a movement that may benon-parallel to the at least one mechanical element.

The beam limiter may include first and second blades, having respectivefirst and second edges positioned in mutual proximity so as to define aslit, through which the beam of the X-rays will pass, at a distancesmaller than mm from the first side of the sample; and first and secondactuators, wherein the method may include shifting, by the first andsecond actuators, the first and second blades along respective, firstand second translation axes so as to adjust a width of the slit.

The sample measurement period and the beam intensity monitoring periodpartially overlap.

There may be provided a non-transitory computer readable medium thatthat may store instructions for holding a sample by a mount; directingan x-ray beam toward a first side of the sample; detecting, during asample measurement period and by a detector positioned downstream to asecond side of the sample, at least a part of x-rays that have beentransmitted through the sample and exited through the second side; anddetecting at least a part of the x-ray beam before the x-ray beamreaches the sample, during a beam intensity monitoring period and by anx-ray intensity detector positioned at a measurement position that maybe located between the x-ray source and the first side of the sample.

There may be provided an x-ray apparatus that may include a mount thatmay be configured to hold a sample; an x-ray source that may beconfigured to direct an x-ray beam toward a first side of the sample; asmall angle x-ray scattering (SAXS) detector that may be positioneddownstream to a second side of the sample, and configured to detect atleast a part of a SAXS pattern formed by x-rays that have beentransmitted through the sample and exited through the second side; andan x-ray fluorescence (XRF) detector that may be configured to detectfluorescent x-rays emitted from the sample; wherein the XRF detector mayinclude an aperture.

The XRF sensor may be positioned upstream to the first side of thesample.

The XRF detector may include an aperture and wherein the x-ray sourcemay be configured to direct the x-ray beam to pass through the aperture.

The XRF detector may be located within less than five millimeters fromthe first side of the sample.

The XRF sensor may be positioned downstream to the second side of thesample.

The aperture may be shaped and sized to enable the at least part of theSAXS pattern to reach the SAXS detector.

The apparatus may include an additional x-ray source that may beconfigured to direct another x-ray beam to pass through the aperture.

The XRF detector may be shaped and positioned to detect fluorescentx-rays emitted from the sample over a large solid angle.

The XRF detector may include at least one independent radiation sensingsegment.

The XRF detector may include at least one independent silicon driftdetector.

There may be provided a method that may include holding a sample by amount; directing an x-ray beam toward a first side of the sample;detecting, by a small angle x-ray scattering (SAXS) detector that may bepositioned downstream to a second side of the sample, at least a part ofa SAXS pattern formed by x-rays that have been transmitted through thesample and exited through the second side; and detecting, by an x-rayfluorescence (XRF) detector, fluorescent x-rays emitted from the sample;wherein the XRF detector may include an aperture.

The XRF sensor may be positioned upstream to the first side of thesample.

The XRF detector may include an aperture and wherein the method mayinclude directing, by the x-ray source, the x-ray beam to pass throughthe aperture.

The XRF detector may be located within less than five millimeters fromthe first side of the sample.

The XRF sensor may be positioned downstream to the second side of thesample.

The aperture may be shaped and sized to enable the at least part of theSAXS pattern to reach the SAXS detector.

The apparatus may include an additional x-ray source that may beconfigured to direct another x-ray beam to pass through the aperture.

The XRF detector may be shaped and positioned to detect fluorescentx-rays emitted from the sample over a large solid angle.

The XRF detector may include at least one independent radiation sensingsegment.

The XRF detector may include at least one independent silicon driftdetector. There may be provided a non-transitory computer readablemedium that that may store instructions for holding a sample by a mount;directing an x-ray beam toward a first side of the sample; detecting, bya small angle x-ray scattering (SAXS) detector that may be positioneddownstream to a second side of the sample, at least a part of a SAXSpattern formed by x-rays that have been transmitted through the sampleand exited through the second side; and detecting, by an x-rayfluorescence (XRF) detector, fluorescent x-rays emitted from the sample;wherein the XRF detector may include an aperture.

There may be provided a method that for determining an orientation of anarray of high aspect ratio (HAR) structures of a sample, the method mayinclude obtaining different small angle x-ray scattering (SAXS) patternsfor at least one out of different angular relationships or in-planespatial relationships between the sample and an x-ray beam thatilluminates the sample; wherein each SAXS pattern represents an angularintensity distribution of scattered x-ray detected by a SAXS sensor;calculating, for at least some of the different SAXS patterns, at leastone sum of intensities within at least one angular range of the angularintensity distribution to provide a first plurality of sums; anddetermining the orientation of the array of HAR holes based at least onthe first plurality of sums.

The determining may include comparing the first plurality of sums toreference sums that may be associated with known orientations of thearray of HAR holes.

The calculating may include calculating the at least one sum ofintensity within the at least one angular range for all of the differentSAXS patterns.

The calculating may include calculating for one or more different SAXSpatterns, two or more sums of intensities within two or more angularranges of the angular intensity distribution.

The obtaining of the different SAXS patterns may include rotating thesample in relation to an x-ray beam that illuminates the sample toprovide the different SAXS patterns.

The obtaining of the different SAXS patterns may include rotating, inrelation to the sample, an x-ray beam that illuminates the sample toprovide the different SAXS patterns.

There may be provided a non-transitory computer readable medium thatthat may store instructions for obtaining different small angle x-rayscattering (SAXS) patterns for different angular and/or in-plane spatialrelationships between a sample that may include an array of high aspectratio (HAR) holes and an x-ray beam that illuminates the sample; whereineach SAXS pattern represents an angular intensity distribution ofscattered x-ray detected by a SAXS sensor; calculating, for at leastsome of the different SAXS patterns, at least one sum of intensitieswithin at least one angular range of the angular intensity distributionto provide a first plurality of sums; and determining an orientation ofthe array of HAR holes based on the first plurality of sums.

The determining may include comparing the first plurality of sums toreference sums that may be associated with known orientations of thearray of HAR holes.

The calculating may include calculating the at least one sum ofintensity within the at least one angular range for all of the differentSAXS patterns.

The calculating may include calculating for one or more different SAXSpatterns, two or more sums of intensities within two or more angularranges of the angular intensity distribution.

The obtaining of the different SAXS patterns may include rotating thesample in relation to an x-ray beam that illuminates the sample toprovide the different SAXS patterns.

The obtaining of the different SAXS patterns may include rotating, inrelation to the sample, an x-ray beam that illuminates the sample toprovide the different SAXS patterns.

There may be provided an apparatus that may include a mount that may beconfigured to hold a sample that may include an array of high aspectratio (HAR) holes; x-ray optics that may be configured to obtaindifferent small angle x-ray scattering (SAXS) patterns for differentangular relationships between the sample and an x-ray beam thatilluminates the sample; wherein each SAXS pattern represents an angularintensity distribution of scattered x-ray detected by a SAXS sensor; aprocessor that may be configured to (a) calculate, for at least some ofthe different SAXS patterns, at least one sum of intensities within atleast one angular range of the angular intensity distribution to providea first plurality of sums; and (b) determine the orientation of thearray of HAR holes based on the first plurality of sums.

The determining may include comparing the first plurality of sums toreference sums that may be associated with known orientations of thearray of HAR holes.

The calculating may include calculating the at least one sum ofintensity within the at least one angular range for all of the differentSAXS patterns.

The calculating may include calculating for one or more different SAXSpatterns, two or more sums of intensities within two or more angularranges of the angular intensity distribution.

The obtaining of the different SAXS patterns may include rotating thesample in relation to an x-ray beam that illuminates the sample toprovide the different SAXS patterns.

The obtaining of the different SAXS patterns may include rotating, inrelation to the sample, an x-ray beam that illuminates the sample toprovide the different SAXS patterns.

There may be provided a method that for determining an orientation andshape of an array of high aspect ratio (HAR) structures of a sample, themethod may include illuminating the sample with an x-ray beam, while thex-ray beam may be substantially parallel to the HAR holes of the array;wherein the sample further may include one or more additional repetitivestructures; wherein an aspect ratio of structural elements that form theone or more additional repetitive structures may be much smaller than anaspect ratio of the HAR holes; sensing a first small angle x-rayscattering (SAXS) pattern by a SAXS detector; changing a spatialrelationship between the sample and an optical axis of the x-ray beam;illuminating the sample with the x-ray beam, while the x-ray beam may besubstantially oblique to the HAR holes of the array; sensing a secondSAXS pattern by the SAXS detector; determining a relationship betweenthe first and second SAXS patterns; and generating information about thearray of HAR holes based on the relationship between the first andsecond SAXS patterns.

The one or more additional repetitive structure may be substantiallyparallel to the array of HAR holes.

The changing of the spatial relationship may include changing a spatialrelationship between the x-ray beam and the sample to substantiallyeliminate an effect of the array on the second SAXS pattern.

The changing of the spatial relationship may include rotating thesample.

The changing of the spatial relationship may include rotating the x-raybeam.

The method may include estimating, based on the relationship, a combinedeffect of the additional repetitive structures and backscattered x-rayradiation.

The x-ray beam may be substantially parallel to the HAR holes of thearray by deviating up to two degrees from a prefect alignment with alongitudinal axis of the HAR holes.

There may be provided a non-transitory computer readable medium thatthat may store instructions for illuminating a sample with a x-ray beam,while the x-ray beam may be substantially parallel to high aspect ratio(HAR) holes of an array of HAR holes that belong to the sample; whereinthe sample further may include one or more additional repetitivestructures; wherein an aspect ratio of structural elements that form theone or more additional repetitive structures may be much smaller than anaspect ratio of the HAR holes; sensing a first small angle x-rayscattering (SAXS) pattern by a SAXS detector; changing a spatialrelationship between the sample and an optical axis of the x-ray beam;illuminating the sample with the x-ray beam, while the x-ray beam may besubstantially oblique to the HAR holes of the array; sensing a secondSAXS pattern by the SAXS detector; determining a relationship betweenthe first and second SAXS patterns; and generating information about thearray of HAR holes based on the relationship between the first andsecond SAXS patterns.

The one or more additional repetitive structure may be substantiallyparallel to the array of HAR holes.

The changing of the spatial relationship may include changing a spatialrelationship between the x-ray beam and the sample to substantiallyeliminate an effect of the array on the second SAXS pattern.

The changing of the spatial relationship may include rotating thesample.

The changing of the spatial relationship may include rotating the x-raybeam.

The non-transitory computer readable medium that may store instructionsfor estimating, based on the relationship, a combined effect of theadditional repetitive structures and backscattered x-ray radiation.

The x-ray beam may be substantially parallel to the HAR holes of thearray by deviating up to two degrees from a prefect alignment with alongitudinal axis of the HAR holes.

There may be provided an apparatus that may include a mount that may beconfigured to hold a sample that may include an array of high aspectratio (HAR) holes and may include one or more additional repetitivestructures; wherein an aspect ratio of structural elements that form theone or more additional repetitive structures may be much smaller than anaspect ratio of the HAR holes; x-ray optics that may be configured to(i) illuminate a sample with a x-ray beam, while the x-ray beam may besubstantially parallel to high aspect ratio (HAR) holes of an array ofHAR holes, (ii) sense a first small angle x-ray scattering (SAXS)pattern by a SAXS detector; (iii) change a spatial relationship betweenthe sample and an optical axis of the x-ray beam; (iv) illuminate thesample with the x-ray beam, while the x-ray beam may be substantiallyoblique to the HAR holes of the array; and (v) sense a second SAXSpattern by the SAXS detector; and a processor that may be configured to(i) determine a relationship between the first and second SAXS patterns;and (ii) generate information about the array of HAR holes based on therelationship between the first and second SAXS patterns.

The one or more additional repetitive structure may be substantiallyparallel to the array of HAR holes.

The changing of the spatial relationship may include changing a spatialrelationship between the x-ray beam and the sample to substantiallyeliminate an effect of the array on the second SAXS pattern.

The changing of the spatial relationship may include rotating thesample.

The changing of the spatial relationship may include rotating the x-raybeam.

The apparatus may include estimating, based on the relationship, acombined effect of the additional repetitive structures andbackscattered x-ray radiation.

The x-ray beam may be substantially parallel to the HAR holes of thearray by deviating up to two degrees from a prefect alignment with alongitudinal axis of the HAR holes.

There may be provided a method that for evaluating a sample that mayinclude an array of structural elements, the method may includeobtaining a first small angle x-ray scattering (SAXS) pattern for afirst angular relationship between the sample and an x-ray beam thatexhibits a first collimation value; obtaining a second SAXS pattern fora second angular relationship between the sample and the x-ray beam,while the x-ray beam exhibits a second collimation value that differsfrom the first collimation value; wherein the second angularrelationship differs from the first angular relationship; and whereinthe obtaining of the first and second SAXS patterns may includesubstantially maintaining an area of a cross section of the x-ray on afirst side of the sample during the obtaining of the first and secondSAXS patterns.

The method may include obtaining at least one additional SAXS patternfor at least one additional angular relationship between the sample andthe x-ray beam; wherein each additional angular relationship, the firstand second angular relationships differ from each other; wherein theobtaining of each additional SAXS pattern may include substantiallymaintaining the area of the cross section of the x-ray on the first sideof the sample while changing the collimation of the x-ray beam.

The method may include evaluating the sample based, at least, on thefirst and second SAXS patterns.

The obtaining of the first SAXS pattern and the obtaining of the secondSAXS pattern further differ from each other by an intensity of the x-raybeam.

The cross section of the x-ray beam has a circular shape and wherein adifference between the first collimation value and the secondcollimation value determines an eccentricity of diffraction orders offirst and second SAXS patterns.

The first angular relationship may be a first angle of illumination thesecond angular relationship may be a second angle of illumination,wherein the second angle of illumination exceeds the first angle ofillumination and wherein the first collimation value represents an x-raybeam that may be more collimated than an x-ray beam having the secondcollimation value.

The method may include determining the second collimation value based onat least signal to noise ratio associated with the second SAXS pattern.

The method may include determining the second collimation value based onat least an expected overlap between lobes of the second SAXS pattern.

The method may include determining the second collimation value based oninformation obtained from the first SAXS pattern.

The method may include determining the second collimation value based ona priority or importance of the array of structural elements.

There may be provided a non-transitory computer readable medium thatthat may store instructions for obtaining a first small angle x-rayscattering (SAXS) pattern for a first angular relationship between asample and an x-ray beam that exhibits a first collimation value;wherein the sample may include an array of structural elements;obtaining a second SAXS pattern for a second angular relationshipbetween the sample and the x-ray beam, while the x-ray beam exhibits asecond collimation value that differs from the first collimation value;wherein the second angular relationship differs from the first angularrelationship; and wherein the obtaining of the first and second SAXSpatterns may include substantially maintaining an area of a crosssection of the x-ray on a first side of the sample during the obtainingof the first and second SAXS patterns.

The non-transitory computer readable medium that may store instructionsfor obtaining at least one additional SAXS pattern for at least oneadditional angular relationship between the sample and the x-ray beam;wherein each additional angular relationship, the first and secondangular relationships differ from each other; wherein the obtaining ofeach additional SAXS pattern may include substantially maintaining thearea of the cross section of the x-ray on the first side of the samplewhile changing the collimation of the x-ray beam.

The non-transitory computer readable medium that may store instructionsfor evaluating the sample based, at least, on the first and second SAXSpatterns.

The obtaining of the first SAXS pattern and the obtaining of the secondSAXS pattern further differ from each other by an intensity of the x-raybeam.

The cross section of the x-ray beam has a circular shape and wherein adifference between the first collimation value and the secondcollimation value determines an eccentricity of diffraction orders offirst and second SAXS patterns.

The first angular relationship may be a first angle of illumination thesecond angular relationship may be a second angle of illumination,wherein the second angle of illumination exceeds the first angle ofillumination and wherein the first collimation value represents an x-raybeam that may be more collimated than an x-ray beam having the secondcollimation value.

The non-transitory computer readable medium that may store instructionsfor determining the second collimation value based on at least signal tonoise ratio associated with the second SAXS pattern.

The non-transitory computer readable medium that may store instructionsfor determining the second collimation value based on at least anexpected overlap between lobes of the second SAXS pattern.

The non-transitory computer readable medium that may store instructionsfor determining the second collimation value based on informationobtained from the first SAXS pattern.

The non-transitory computer readable medium that may store instructionsfor determining the second collimation value based on a priority orimportance of the array of structural elements.

There may be provided an x-ray apparatus that may include a mount forholding a sample that may include an array of structural elements; x-rayoptics that may be configured to obtain a first small angle x-rayscattering (SAXS) pattern for a first angular relationship between thesample and an x-ray beam that exhibits a first collimation value; andobtain a second SAXS pattern for a second angular relationship betweenthe sample and the x-ray beam, while the x-ray beam exhibits a secondcollimation value that differs from the first collimation value; whereinthe second angular relationship differs from the first angularrelationship; wherein an obtaining of the first and second SAXS patternsmay include substantially maintaining an area of a cross section of thex-ray on a first side of the sample during the obtaining of the firstand second SAXS patterns.

The x-ray apparatus that may include a processor that may be configuredto evaluate the sample based, at least, on the first and second SAXSpatterns.

The processor may be configured to determine the second collimationvalue based on at least signal to noise ratio associated with the secondSAXS pattern.

The processor may be configured to determine the second collimationvalue based on at least an expected overlap between lobes of the secondSAXS pattern.

The processor may be configured to determine the second collimationvalue based on information obtained from the first SAXS pattern.

The processor may be configured to determine the second collimationvalue based on a priority or importance of the array of structuralelements.

The apparatus that may be configured to obtain at least one additionalSAXS pattern for at least one additional angular relationship betweenthe sample and the x-ray beam; wherein each additional angularrelationship, the first and second angular relationships differ fromeach other; wherein the obtaining of each additional SAXS pattern mayinclude substantially maintaining the area of the cross section of thex-ray on the first side of the sample while changing the collimation ofthe x-ray beam.

The obtaining of the first SAXS pattern and the obtaining of the secondSAXS pattern further differ from each other by an intensity of the x-raybeam.

The cross section of the x-ray beam has a circular shape and wherein adifference between the first collimation value and the secondcollimation value determines an eccentricity of diffraction orders offirst and second SAXS patterns.

The first angular relationship may be a first angle of illumination thesecond angular relationship may be a second angle of illumination,wherein the second angle of illumination exceeds the first angle ofillumination and wherein the first collimation value represents an x-raybeam that may be more collimated than an x-ray beam having the secondcollimation value.

The term “configured to” may mean “constructed and arranged to”.

Any reference to “comprising” should be applied mutatis mutandis to“consisting” and to “consisting essentially of”.

Any combination of any step of any method can be provided. Thus—stepsfrom two or more methods can be a part of a method covered by thisapplication.

Any combination of any instructions stored in any non-transitorycomputer readable medium may be provided. Thus, a computer readablemedium may store instructions for executing any combinations of steps ofone or more methods illustrated in the specification.

Any combination of any components (for example—sensors, optics,mechanical elements, detectors, and the like) illustrated in theapplication may be provided.

Any reference to any one of a method, an apparatus (including an x-rayapparatus), and a non-transitory computer readable medium should beapplied mutatis mutandis to any other one of the method, apparatus(including the x-ray apparatus), and the non-transitory computerreadable medium.

The drawings may be of scale or may not be of scale.

Although the embodiments described herein mainly address X-ray analysisof single-crystal, polycrystalline or amorphous samples, such assemiconductor wafers, the methods and systems described herein can alsobe used in other technological of applications of arrays ofnanostructures.

It will thus be appreciated that the embodiments described above arecited by way of example, and that the present invention is not limitedto what has been particularly shown and described hereinabove. Rather,the scope of the present invention includes both combinations andsub-combinations of the various features described hereinabove, as wellas variations and modifications thereof which would occur to personsskilled in the art upon reading the foregoing description and which arenot disclosed in the prior art. Documents incorporated by reference inthe present patent application are to be considered an integral part ofthe application except that to the extent any terms are defined in theseincorporated documents in a manner that conflicts with the definitionsmade explicitly or implicitly in the present specification, only thedefinitions in the present specification should be considered.

The invention claimed is:
 1. A method for evaluating an array of highaspect ratio (HAR) structures on a sample, the method comprises:illuminating the sample with an x-ray beam along a first axis parallelto within two degrees to the HAR structures in the array; sensing afirst pattern of small angle x-ray scattering (SAXS) scattered from thesample while illuminating the sample along the first axis; illuminatingthe sample with the x-ray beam along a second axis that is oblique tothe HAR structures in the array; sensing a second pattern of the SAXSscattered from the sample while illuminating the sample along the secondaxis; and extracting information with respect to the HAR structuresbased on the first and second patterns by removing from the firstpattern of the SAXS a contribution of one or more additional repetitivestructures on the substrate having an aspect ratio smaller than the HARstructures, responsively to a sensitivity of the second pattern torotation of the second axis.
 2. The method according to claim 1, whereinthe HAR structures comprise holes having an aspect ratio exceeding 10:1.3. The method according to claim 2, wherein the second axis deviates byat least three degrees from alignment with the holes.
 4. The methodaccording to claim 1, wherein extracting the information comprisessubtracting the second pattern from the first pattern.
 5. The methodaccording to claim 1, wherein extracting the information comprisesgenerating a model of background scattering responsively to the secondpattern, and applying the model in analyzing a contribution of the HARstructures to the first pattern.
 6. The method according to claim 1,wherein extracting the information comprises removing from the firstpattern of the SAXS a contribution of backscattered X-rays.
 7. Themethod according to claim 1, wherein illuminating the sample with thex-ray beam along the second axis comprises setting an angle of thesecond axis so as to eliminate from the second pattern of the SAXS acontribution of the HAR structures.
 8. The method according to claim 1,wherein illuminating the sample with the x-ray beam along the secondaxis comprises rotating the sample relative to the x-ray beam.
 9. Themethod according to claim 1, wherein illuminating the sample with thex-ray beam along the second axis the changing of the spatialrelationship comprises rotating the x-ray beam relative to the sample.10. A non-transitory computer readable medium that stores instructionsfor: illuminating a sample having an array of high aspect ratio (HAR)structures thereon with an x-ray beam along a first axis parallel towithin two degrees to the HAR structures in the array, sensing a firstpattern of small angle x-ray scattering (SAXS) scattered from the samplewhile illuminating the sample along the first axis, illuminating thesample with the x-ray beam along a second axis that is oblique to theHAR structures in the array, sensing a second pattern of the SAXSscattered from the sample while illuminating the sample along the secondaxis, and extracting information with respect to the HAR structuresbased on the first and second patterns by removing from the firstpattern of the SAXS a contribution of one or more additional repetitivestructures on the substrate having an aspect ratio smaller than the HARstructures, responsively to a sensitivity of the second pattern torotation of the second axis.
 11. An apparatus, comprising: a mountconfigured to hold a sample that includes an array of high aspect ratio(HAR) structures; x-ray optics configured to illuminate the sample inthe mount with an x-ray beam along a first axis parallel to within twodegrees to the HAR structures in the array and along a second axis thatis oblique to the HAR structures in the array; a small angle x-rayscattering (SAXS) detector, configured to sense a first pattern of SAXSscattered from the sample while illuminating the sample along the firstaxis and a second pattern of the SAXS scattered from the sample whileilluminating the sample along the second axis; and a processorconfigured to extract information with respect to the HAR structuresbased on the first and second patterns by removing from the firstpattern of the SAXS a contribution of one or more additional repetitivestructures on the substrate having an aspect ratio smaller than the HARstructures, responsively to a sensitivity of the second pattern torotation of the second axis.
 12. The apparatus according to claim 11,wherein the HAR structures comprise holes having an aspect ratioexceeding 10:1.
 13. The apparatus according to claim 12, wherein thesecond axis deviates by at least three degrees from alignment with theholes.
 14. The apparatus according to claim 11, wherein the processor isconfigured to subtract the second pattern from the first pattern. 15.The apparatus according to claim 11, wherein the processor is configuredto generate a model of background scattering responsively to the secondpattern, and to apply the model in analyzing a contribution of the HARstructures to the first pattern.
 16. The apparatus according to claim11, wherein the processor is configured, using the second pattern, toremove from the first pattern of the SAXS a contribution ofbackscattered X-rays.
 17. The apparatus according to claim 11, whereinilluminating the sample with the x-ray beam along the second axiscomprises setting an angle of the second axis so as to eliminate fromthe second pattern of the SAXS a contribution of the HAR structures. 18.The apparatus according to claim 11, wherein illuminating the samplewith the x-ray beam along the second axis comprises rotating the mountrelative to the x-ray beam.
 19. The apparatus according to claim 11,wherein illuminating the sample with the x-ray beam along the secondaxis the changing of the spatial relationship comprises rotating thex-ray beam relative to the sample.